test(dsh): verify observer with Cordis sessions

[mikamikasuki]

Goal And Delivered Outcome

• Outcome basis / optional anchor: Existing public task [Task][RFC]: Qualify observer-first reliability diagnostics and governed delivery #5211.
• Goal/source and gap: The observer tests registered fake session/context objects, so they did not exercise Cordis disposal or native DSH session event publication. The task's public follow-up identifies real Cordis and DSH synthetic publication as the next bounded conformance slice.
• Observable before → after, with the validation row that proves it: Before, the suite did not cover a live Cordis Context with DSH SessionStore lifecycle events. After, the new integration test creates a session, appends a synthetic user message, disposes the session store and context, then verifies the flushed ledger envelopes and counters; see the integration and unit validation rows.
• Issue/task and intended base: Related to [Task][RFC]: Qualify observer-first reliability diagnostics and governed delivery #5211; base main at 3596467d6e5b3bbb7fc32603a1841e9170b7c4f6.

Author Declaration

• Written by: model_agent — GPT-6 (OpenAI)

Implemented against

• Specification and revision: RFC §10.5 and §12; bounded public test gap in #5211 follow-up.
• Criteria:

Criterion (spec clause)	Disposition	Symbol / path	Test or command
#5211 follow-up: exercise real Cordis lifecycle and native DSH synthetic event publication	implemented	packages/dsh-loopx-plugin/tests/observer.spec.ts	pnpm --dir packages/dsh-loopx-plugin test
RFC §12: deterministic fixture for a real harness event source; this PR adds the bounded DSH session API slice only	implemented	packages/dsh-loopx-plugin/tests/observer.spec.ts	pnpm --dir packages/dsh-loopx-plugin test

• Self-check before submission: Reviewed the single-file diff, task follow-up and RFC scope. Ran the package test suite and all three package TypeScript checks. This synthetic test does not claim a live DSH run or P0 qualification.

Scope And Continuation

• Completed scope and remaining work: Adds a test-only conformance case covering Cordis context disposal, DSH session start/message/disposal events and observer ledger flush. The broader [Task][RFC]: Qualify observer-first reliability diagnostics and governed delivery #5211 acceptance remains open, including eligible C0/C1 evidence, a live DSH observer run, overhead measurements and retention/deletion acceptance.
• Slice boundary / successor: Complete within this bounded test slice; broader qualification remains with [Task][RFC]: Qualify observer-first reliability diagnostics and governed delivery #5211.

Validation

• Tested revision: a7056166c3218eb85ecc781817c235d63389df24
• Run state: finished
• Input classes: synthetic

Check kind	Result	Public-safe evidence / limitation
static	passed	tsc -p tsconfig.host.json --noEmit, tsc -p tsconfig.client.json --noEmit, and tsc -p tsconfig.tests.json passed.
unit	passed	pnpm --dir packages/dsh-loopx-plugin test: 11 files, 207 tests passed.
integration	passed	The new test uses actual Cordis Context and DSH SessionStore APIs with synthetic session/message data, then verifies three ledger event envelopes and zero rejected events/failures. It is not a live DSH runner test.
manual	passed	git diff --check passed; the final diff contains only the focused observer test.

• Coverage and gaps: Does not qualify a live DSH run, C0/C1, observer overhead, P0 exit, deployment or retention policy. No production code or runtime behavior changes.

Frontend / Visual Evidence

• UI impact: none
• Before: N/A
• After: N/A
• States and viewports shown: N/A
• Source data: synthetic
• Attention review: No user interface changes.

Type of Change

• Bug fix
• New feature
• Breaking change
• Refactoring (no functional changes)
• Documentation update
• Test update

LoopX Area

• Control plane (goals, todos, quota, scheduler, registry, runtime)

• Benchmark boundary (adapters, runners, verifiers, scoring, evidence)

• Capability or extension (providers, adapters, skills)

• Public docs or presentation surface (README, protocols, dashboard)

• Build, packaging, installer, or CI

• Host or runtime integration

• Direction / acceptance reference, when applicable: Reliability diagnostics S10/S11/S13, bounded public test slice under [Task][RFC]: Qualify observer-first reliability diagnostics and governed delivery #5211.

Shared-authority RFC fixture impact

N/A — this change adds no shared Goal Authority fixture or provider conformance arm.

Boundary Checklist

• Neither the diff nor this PR body/comments/attachments disclose private state, credentials, raw traces or verifier output, internal links, or local machine paths.
• I did not duplicate maintainer-owned benchmark work.
• I kept the change scoped to the linked task.
• I completed the visual evidence section for UI changes, or marked UI impact none.
• Every commit includes a DCO Signed-off-by trailer.