feat(runtime): persist compute inventory snapshots

[tiammomo]

Closes #25

Persist validated Runtime Adapter Compute observations as immutable PostgreSQL history and derive latest freshness from server policy.

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Adds migration 0014, aligned in-memory semantics, idempotent exact retries, fail-closed identity/time conflicts, canonical nanosecond observation keys, bounded future skew and stale-after policy. The PostgreSQL round-trip follows the existing postgres_state_ CI selection; no protected workflow, registry, scheduler, route, UI, credential, mutation, or local-inference-stack change.

Verified with scripts/check-all.sh.

Areas for careful review:

• No known behavior changes outside the reported bug.

Implementation assistance: an external coding workspace was used to prepare the change and its
tests. tiammomo reviewed the final diff, understands it, and takes responsibility
for this contribution.