feat(replay): record runtime identity; label compatibility; analyse first divergence

Snapshots, replays and experiments now record the runtime they ran under:
build (module version, VCS commit, modified tree, commit time, Go version,
platform), schema version, a digest of the non-secret configuration that
ignores secret and credential changes, personality version, policy digest,
model routing including per-mind overrides, prompt versions, deterministic
subsystem versions and timezone. A replay compares its identity with the
snapshot's and is an exact-candidate, a different-build (differences
listed) or incompatible (schema differs; the replay stops before running).
The first non-exact step is analysed into events only in the recording,
events only in the replay, and the components they belong to, labelled as
inferred; live model calls are named as their own source of difference.
Migration 0022 is additive; unrecorded identities are reported as such.

CHANGELOG.md

@@ -10,6 +10,7 @@ All notable changes to Noema are recorded here. Format follows Keep a Changelog;
 - Security suite: SQL-injection effect test, static allow-list scan for assembled SQL, deceived-mind authority test, garbage model output test, self-preservation vocabulary test; threat model rewritten so every verification cites a test that asserts the claim.
 
 ### Added
+- Runtime identity: snapshots, replays and experiments record build (commit, modified tree, Go version, platform), schema version, a secret-free configuration digest, personality version, policy digest, model routing, prompt versions, deterministic subsystem versions and timezone. Replays compare identities and label themselves exact-candidate, different-build or incompatible (the last is never run), and analyse the first divergence by component. Migration 0022.
 - Contextual source reliability: a per-(source, domain) record updated only by prediction outcomes and operator corrections, adjusting evidence credibility in that domain once three outcomes exist; never global. Shown on belief pages. Migration 0021.
 - Temporal beliefs: every belief has a temporal scope (persistent, transient, unknown, classified deterministically), an observation time and, for transient states, a validity interval. A later observation that a transient state changed closes the earlier belief (valid_until, superseded, score unchanged) instead of contesting it; simultaneous conflicts and persistent propositions still contradict. Introspection reports what was true and when. Migration 0020.
 - Confidence semantics: every breakdown states that the number is an uncalibrated epistemic score; belief detail adds a calibrated estimate from the mind's resolved predictions when at least twenty were decided in the same range (otherwise says why not) and names the primary uncertainty deterministically. `docs/beliefs.md` defines every epistemic number.