fix(engine): return the exiled "rest" to the library bottom for exile-until chains (Jodah #5277, #5292)

[shin-core]

Fixes #5277 and fixes #5292 (both claimed there first, with the full root-cause breakdown). Verified Jodah's Oracle text and rulings on Scryfall before designing:

• "If you exile your entire library without exiling a legendary nonland card with lesser mana value, you will randomize the exiled cards and they again become your library, ending the effect."
• "If you choose not to cast the card, it remains in exile. The rest of the cards will be put on the bottom of your library in a random order."

The bugs (three compounding, one pipeline)

Jodah's trigger parses to ExileFromTopUntil { NextMatches } → optional CastFromZone { ParentTarget } → PutAtLibraryPosition { TrackedSet(0), Bottom }. The exiled pile got stranded in exile in every path:

1. No match (jodah, the unifer makes you lose the game. — If you chain 4 or 5 times you just lose the game. #5277 — the game loss): exile_from_top_until.rs ran the sub-chain only if let Some(hit). Exhausting the library skipped the bottom-cleanup entirely; repeated triggers shrank the real library until an engine-caused deck-out.
2. Dead cleanup channel (Jodah the unifier — After the cards are exiled, they do not return to the bottom of the library  #5292): the cleanup's TrackedSet(0) is never published by the exile-until resolver, and put_on_top.rs's tracked-set collection scans zone == Library only — never Exile. So even when the cleanup ran, it collected zero cards.
3. The working Chaos Wand class routes this through ExiledBySource (which does scan Exile) via normalize_linked_exile_cast_bottom_cleanup, which also wires the cleanup as the cast's else_ability — but its gate requires the cast/cleanup target to already reference ExiledBySource, which Jodah's ParentTarget cast + TrackedSet cleanup never satisfies.

The fix, per layer

• Parser (lower.rs, wired at both assembly call sites): a head-aware companion gate, is_exile_until_cast_bottom_cleanup. When the chain head is ExileFromTopUntil { NextMatches } — the discriminator that keeps the Dig/Expressive-Iteration class (whose rest-cards never left the library) on its correct TrackedSet library-scan — the bottom-cleanup is normalized to And { ExiledBySource, Typed(DistinctFrom { ParentTarget }) } and wired as the optional cast's else_ability (the proven Chaos Wand shape). The DistinctFrom { ParentTarget } leg (reusing the feat(engine): Radiance color fan-out damage (Cleansing Beam #5244) #5470 building block) encodes the decline ruling: the un-cast hit remains in exile, only "the rest" is swept. It fails open with no bound hit, so the no-match case returns everything — exactly the ruling.
• put_on_top.rs: the ExiledBySource branch entries (exile-zone scan gate, random-order placement, exile-link retirement) generalize from an exact match to references_exiled_by_source() so the And-composed form reaches the scan; the collected-targets seed is forced empty for such filters so an inherited hit target can't bypass the scan + exclusion.
• exile_from_top_until.rs: on no hit, the resolver walks the sub-chain for the first ExiledBySource-referencing cleanup link and resolves it with cleared targets — the whole pile returns to the library bottom.
• effects/mod.rs: filter_refs_parent_target now recognizes DistinctFrom { reference: ParentTarget } inside a Typed filter's properties, so the decline branch inherits ability.targets and the declined hit is excluded by identity.

Tests (each fails on revert of its seam)

• jodah_no_hit_returns_all_exiled_cards_to_library — the jodah, the unifer makes you lose the game. — If you chain 4 or 5 times you just lose the game. #5277 loss: library exhausted, ALL cards return (revert → all stay in exile).
• jodah_hit_accept_casts_hit_and_returns_misses — hit on the stack, misses returned (revert of the seed fix → hit swept to library).
• jodah_hit_decline_leaves_hit_in_exile_returns_misses — the discriminating Jodah-vs-Chaos-Wand ruling: declined hit stays in exile (revert of the predicate extension → hit wrongly returns).
• jodah_parse_lowers_the_rest_cleanup — verbatim Oracle text lowers to the And-composed cleanup on BOTH sub_ability and else_ability, zero Unimplemented (positive reach-guard).
• Regressions: both Chaos Wand decline/accept tests and the Dig/Expressive-Iteration class tests stay green unchanged.

Verification

• Full engine lib suite: 16170 passed, 0 failed. Clippy: clean. cargo fmt: clean. Parser combinator gate: exit 0.
• CR annotations (109.1, 406.6, 608.2c, 701.13a) all grep-verified against docs/MagicCompRules.txt.

🤖 Generated with Claude Code

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[github-actions]

Parse changes introduced by this PR · 3 card(s), 3 signature(s) (baseline: main 9a156beade96)

3 card(s) · ability/PutAtLibraryPosition · added: PutAtLibraryPosition (count=Fixed { value: 0 }, position=Bottom, target=cards exiled by source + other than target)

Examples: Jodah, the Unifier, Ryan Sinclair, The Day of the Doctor

3 card(s) · ability/PutAtLibraryPosition · field count: Fixed { value: 1 } → Fixed { value: 0 }

Examples: Jodah, the Unifier, Ryan Sinclair, The Day of the Doctor

3 card(s) · ability/PutAtLibraryPosition · field target: tracked set #0 → cards exiled by source + other than target

Examples: Jodah, the Unifier, Ryan Sinclair, The Day of the Doctor

1 card(s) had Oracle-text changes (errata/reprint) — excluded as non-parser.

[matthewevans]

Approve — the Jodah-class exile-until cleanup now preserves the selected-hit provenance across no-hit, cast, and decline resolution paths.

🔴 Blocker

• None. The maintainer port’s stale import was repaired on 1b4efa2; all required current-head checks are green.

🟡 Non-blocking

• Gemini is quota-limited this session; the local adversarial review covered the current head and the full CI/parse artifact is available.

✅ Clean

• The parser reuses ExiledBySource, DistinctFrom { ParentTarget }, and the existing Chaos-Wand cleanup shape rather than inventing a second cleanup channel.
• Runtime regressions discriminate the library-exhausted, accepted-hit, and declined-hit cases; the declined hit remains exiled while only the rest return.
• The current parse artifact is limited to Jodah, Ryan Sinclair, and The Day of the Doctor (three expected cleanup signatures).

Recommendation: approve and enqueue as bug.