feat: support --settle on scroll and back (generic-route settle observation) - #1653

Two sessions independently built #1638 (PR #1650 and PR #1653) and converged
on the same architecture — trait in the registry, one engine with two entry
points, runtime-command seam, lazy import, preserve-daemon, stored-baseline
honesty. #1650 continues; this folds in what #1653 did better:

- The agent-facing help core loop (cli-help.ts) now names scroll and back as
  settle-capable. Without this, the benchmarked closed-grammar help line kept
  instructing agents that --settle is only for press/click/fill/longpress —
  actively steering the AppControlBench models away from what #1638 shipped.
- issueSettleRefs moves into session-snapshot.ts, beside the partial-frame
  primitive it wraps, deleting the single-function settle-ref-issuance module.
- Their seam tests: back reader→writer settle plumbing, back CLI settle
  rendering, and a trait-less generic command (home) ignoring a stray settle
  flag rather than observing or rejecting.

What #1650 had that #1653 lacked, for the record: the SETTLE_REF_ISSUING_TOOLS
registry derivation (without it, MCP never pins a scroll/back settle diff's
refs and the partial frame rejects every follow-up), BackCommandResult.settle
in contracts, back's MCP output schema, paste-ready pinned diff refs, and the
docs/changelog/baseline surfaces.

Two sessions independently built #1638 (PR #1650 and PR #1653) and converged
on the same architecture — trait in the registry, one engine with two entry
points, runtime-command seam, lazy import, preserve-daemon, stored-baseline
honesty. #1650 continues; this folds in what #1653 did better:

- The agent-facing help core loop (cli-help.ts) now names scroll and back as
  settle-capable. Without this, the benchmarked closed-grammar help line kept
  instructing agents that --settle is only for press/click/fill/longpress —
  actively steering the AppControlBench models away from what #1638 shipped.
- issueSettleRefs moves into session-snapshot.ts, beside the partial-frame
  primitive it wraps, deleting the single-function settle-ref-issuance module.
- Their seam tests: back reader→writer settle plumbing, back CLI settle
  rendering, and a trait-less generic command (home) ignoring a stray settle
  flag rather than observing or rejecting.

What #1650 had that #1653 lacked, for the record: the SETTLE_REF_ISSUING_TOOLS
registry derivation (without it, MCP never pins a scroll/back settle diff's
refs and the partial frame rejects every follow-up), BackCommandResult.settle
in contracts, back's MCP output schema, paste-ready pinned diff refs, and the
docs/changelog/baseline surfaces.

* feat: support --settle on scroll and back (#1638)

Scroll-then-observe and back-then-observe are legitimate agent pairs, but
the post-action observation registry never grew past the touch commands, so
`--settle` on either was rejected with INVALID_ARGS — burning a tool call
each in AppControlBench's bsky-16.

Both commands now carry the `settle` descriptor trait, and every surface
derives from it rather than a hand list: CLI allowed flags, MCP/SDK input
fields, the flag-sourced timeout envelope, and MCP ref-pinning. The CLI
flag/metadata helpers moved out of the interaction family into
post-action-observation-grammar.ts (back is a system command), and
SETTLE_REF_ISSUING_TOOLS became a derivation — a hand list would have
silently stopped pinning the new commands' refs.

settleAfterInteraction and the new settleObservationCommand are two entry
points over one engine: same loop, storage, hints, and diff bounds, with the
target-less path supplying its own baseline and no proximity point. The
daemon reaches that command through the runtime surface, never by importing
`commands/` (R2) — the same seam the touch handlers use for press/fill —
and generic-settle.ts is loaded through a lazy `await import` returning a
closure, so the interaction runtime subgraph stays out of this dispatcher's
static graph (a static edge folded ~18 files into the daemon-server type
cycle; R10 caught it).

Both of generic-settle's orderings are load-bearing and tested: the baseline
is frozen before dispatch (and before the Android dialog preflight), and the
observation runs after markDeferredInteractionOutcome so settle's first
capture folds in the #1542 stabilization rather than racing it. The ADR 0014
"a settled diff publishes refs" rule moved to settle-ref-issuance.ts, shared
by both routes.

One divergence is deliberate: scroll/back resolve no element, so the diff
baseline is the session's STORED pre-action tree — "settled tree vs the
last tree you observed" — not press's freshly resolved pre-action capture.

Both commands also switch to preserve-daemon on timeout, which changes the
non-settle path too: with --settle their dominant hang mode is now a wedged
accessibility bridge, and a timed-out capture must not reset the daemon and
lose every session (#1105). The reviewed-set gate records it.

Live-validated on an iOS 26.2 simulator (Settings): scroll --settle settled
in 1786ms with a +6/-6 diff carrying fresh refs; back --settle in 771ms with
+15/-6. Alternating cost runs, one call vs the pair it replaces:
scroll 2.9-3.0s vs 5.3-5.6s, back 3.1-3.2s vs 4.7-5.1s. Those include the
#1627 deep-capture extension.

* fix: render settled-diff refs paste-ready in CLI output

A settled diff activates a PARTIAL ref frame (ADR 0014), which admits only
the pinned `@eN~s<gen>` form of the refs it issued. The unchanged-interactive
tail already rendered that way, but the diff's own added lines rendered the
bare `@eN` embedded in the snapshot line — so a CLI caller who copied the
ref the diff just handed them got `plain_ref_requires_complete_frame` and had
to append the generation by hand.

Added lines now render pinned when the response carries `refsGeneration`,
exactly like the tail. Removed lines render verbatim: they name elements that
just left the screen, and `SettleDiffLine` never gives them a ref.

This is not new to scroll/back — press/click/fill/longpress had the same gap
since #1101. MCP was never affected: its ref-pin store rewrites plain refs on
the way in, which is why the model never sees a suffix.

Live: `scroll down --settle` now emits `+ @E14~s218078 [cell] "Game Center"`,
and `press @E14~s218078` copied straight out of that line taps successfully.

* test: record the pinned-diff-ref bytes in the output-economy baseline

Rendering added diff-line refs pinned costs 8 bytes in the two settle CLI
text samples (two `~s<gen>` suffixes). The output-economy baseline is the
tripwire for exactly this, so the increase takes an explicit reviewed waiver
rather than a silent baseline bump — the same one the settled TAIL's pins
already carry, for the same ADR 0014 reason.

Only `bytes` moves: lines, refs, hints, and shape are unchanged, which is the
evidence that this is a suffix on existing refs and not a new payload.

Caught by CI, not locally: `pnpm test:unit` runs unit-core and
subprocess-stub only, while the Coverage lane runs every vitest project.

* test: prove the generic settle degrades when its runtime cannot be built

`createGenericSettleRuntime` catches and returns undefined so an observation
that cannot even start does not fail an action that already succeeded. That
was a claim in a docstring with nothing behind it — the one changed line the
coverage gate reported uncovered (95/96).

The test puts the session in the state the catch exists for: the router
handed us a session that is no longer in the store, so building the settle
runtime throws SESSION_NOT_FOUND. The response keeps its scroll result and
simply carries no settle payload. Removing the try/catch fails it.

* build: teach fallow that vi.mock reaches pinOwnProcessStartTime dynamically

Not from this PR: #1642 added `pinOwnProcessStartTime` on main, and its three
consumers reach it the only way a Vitest module mock can —
`vi.mock(path, async (importOriginal) => (await import('...')).pinOwnProcessStartTime(...))`.
Dependency analysis cannot follow that dynamic import to a consumer, so the
export reads as dead the moment any PR pulls that file into its audit scope.
This PR is the one that did.

The entry records the consumers by path and the reason, matching the
daemon route-handler entry directly above it, which exists for the same
dynamic-`import()` limitation.

* refactor: adopt the best of the parallel #1653 implementation

Two sessions independently built #1638 (PR #1650 and PR #1653) and converged
on the same architecture — trait in the registry, one engine with two entry
points, runtime-command seam, lazy import, preserve-daemon, stored-baseline
honesty. #1650 continues; this folds in what #1653 did better:

- The agent-facing help core loop (cli-help.ts) now names scroll and back as
  settle-capable. Without this, the benchmarked closed-grammar help line kept
  instructing agents that --settle is only for press/click/fill/longpress —
  actively steering the AppControlBench models away from what #1638 shipped.
- issueSettleRefs moves into session-snapshot.ts, beside the partial-frame
  primitive it wraps, deleting the single-function settle-ref-issuance module.
- Their seam tests: back reader→writer settle plumbing, back CLI settle
  rendering, and a trait-less generic command (home) ignoring a stray settle
  flag rather than observing or rejecting.

What #1650 had that #1653 lacked, for the record: the SETTLE_REF_ISSUING_TOOLS
registry derivation (without it, MCP never pins a scroll/back settle diff's
refs and the partial frame rejects every follow-up), BackCommandResult.settle
in contracts, back's MCP output schema, paste-ready pinned diff refs, and the
docs/changelog/baseline surfaces.

* bench: help-conformance case for settled scroll-to-find planning

The #1638 extension of the closed --settle grammar to scroll/back is the
feature's entire payoff — collapsing scroll-then-observe into one call — and
the closed command list is an enumerated N whose enumerator is this bench.
The regex over the help text proves the sentence exists; this case checks
whether a model plans differently because of it.

One focused case, deliberately not coached: a pinned visible-first snapshot
(rendered by formatSnapshotText, pinned by the sample-producers gate) whose
wanted row is summarized off-screen with no ref anywhere in the output. The
tempting pre-#1638 plan is `scroll` plus a separate `snapshot -i`; acceptance
is the single settled call. Scoring was verified against eight plan shapes in
both directions before recording.

Model-backed record (claude-haiku-4-5, 3 trials, current help): 0/3 — but the
decomposition is the finding. Settle eligibility GENERALIZED (3/3 trials put
--settle on scroll unprompted; the mutation-suffix framing concern did not
materialize) and the two-call habit is residual (1/3). All three trials failed
on `scroll @e3 down --settle` — the pre-existing #1366 scroll-takes-no-target
confusion, which the live CLI recovers with a dedicated hint but a single-shot
bench cannot. The recorded gap is therefore a first-30 doc gap (nothing
teaches that scroll takes no target), not a settle-eligibility gap; tuning the
case until it passes would just delete the evidence.