skillscript-runtime v0.16.9

Cluster ring. Four items closing the identity-propagation surface
opened in v0.16.8. v0.16.8 landed SkillMeta.author capture +
HttpMcpConnector per-call header (Level 1 — identity reaches
transport) but honestly declared supports_identity_propagation: false
because per-call headers don't propagate end-to-end against
session-pinning substrates (warm-adopter's 1e1c9305 finding). This
ring lands the structural close: per-identity session keying achieves
Level 2 (distinct ctx.agentId → distinct observable substrate scope),
owner-as-default for all dispatch paths, and a conformance probe that
gates the true claim on probe-wired evidence.

Charter: Perry's 9af842f7 ack + 33fefa0f go-ahead. Empirically
validated against live AMP via warm-adopter's 299c0d20 reference
prototype before charter commit.

1. Overwrite-status preservation in FilesystemSkillStore

store() now reads the last version's persisted status before write
and preserves it on overwrite. Body's # Status: header is rewritten
to match preserved status via existing rewriteStatusHeader. Explicit
metadata.status overrides the persisted value (authority bypass for
substrate operations).

Closes the sibling-class issue to v0.16.8 item 1's author-locking:
the SkillStore IS the trust boundary for both author identity AND
approval state — body-declared status on overwrite was bypassing the
boundary. Now: body declares, store records, persisted state wins on
overwrite, body rewritten to match.

2. Per-identity session keying in HttpMcpConnector

Connector rewrite per warm-adopter's IdentityAwareAmpConnector
reference impl pattern. Each distinct ctx.agentId gets its own
session, pinned to that identity at server-side initialize time.
Map<identity, SessionEntry> with insertion-order LRU eviction
(maxPoolSize config field, bump-on-access for MRU promotion).
StaleSessionError triggers one bounded re-init + retry. Per-identity
pooling activates ONLY when identityHeader is configured — adopters
who don't thread identity get substrate-neutral default-session
behavior.

supports_identity_propagation: true flag flipped on — both Level 1
AND Level 2 achieved against session-pinning substrates including AMP.

3. RuntimeCapabilitiesConformance auto-coverage probe (Level 1 + Level 2)

The flag claim is now gated on adopter-supplied probe evidence. When
ANY registered McpConnector declares
supports_identity_propagation: true in staticCapabilities(), the
conformance suite auto-generates a coverage test that requires BOTH
probes via flagProbes:

• mcpConnectors.<name>.supports_identity_propagation.level1 —
  identity reaches transport (substrate-independent)
• mcpConnectors.<name>.supports_identity_propagation.level2 —
  distinct ctx.agentId yields distinct observable substrate scope
  (substrate-coupled; adopter pattern: identity-pinned mock or live
  substrate)

Closes the structural-honesty gate per 33fefa0f: declaring the flag
without probes is a discipline-only-contract instance. The probe
catches the false-positive scenario warm-adopter flagged — per-call
headers pass Level 1 while silently failing Level 2.

4. Owner-as-default for all cross-author dispatch paths

execute_skill MCP tool already populated ctx.agentId from
SkillMeta.author in v0.16.8. This ring generalizes to the two
remaining dispatch paths:

• executeSkillByName() in src/composition.ts — when a skill inlines
  another via ! call, the child ctx.agentId is set to the called
  skill's author (cross-author = called-skill-author default per
  Perry's fd18e3f7: identity follows the skill).
• dispatchSkill() in src/scheduler.ts — trigger-fired dispatch
  populates ctx.agentId from the loaded skill's metadata.

Dual-identity delegation (caller + callee both threaded) deferred to
v0.17+.

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