docs: portable signed records across AI and agent workflows

[jithinraj]

Summary

Refreshes release metadata, generated release/conformance tables, package version stamps, and the changelog for
the next patch release. Includes three small public documentation hygiene fixes. No schema, registry, wire
format, signing, public API, CLI, package-set, or protocol behavior change.

Scope

• Version stamp 0.15.2 -> 0.15.3: all workspace package versions, scripts/publish-manifest.json,
  specs/kernel/errors.json (version), the MCP server SERVER_VERSION, smithery.yaml pin, the
  @peac/telemetry-otel version source, docs/releases/{facts.json,current.json}, and the conformance tooling
  VERSION constant. The package-surface audit allowlist is advanced to accept the new target.
• Release metadata: docs/releases/facts.json version plus measured metrics.tests / metrics.test_files.
• CHANGELOG: a 0.15.3 entry; the date is kept only on the newest and the first-ever entries, per the
  existing convention.
• Regenerated: packages/kernel/src/errors.generated.ts, error-categories.generated.ts, and
  docs/specs/CONFORMANCE-MATRIX.md from the bumped specs (codegen-drift verified clean). Conformance vector and
  manifest JSON files carry the same version-string bump and are otherwise unchanged.
• Doc hygiene: replaced four em-dash separators in examples/open-model-inference-records/README.md with
  ASCII; tightened the wording in docs/standards/portable-signed-records-evidence-primitive.md
  ("records what was reported", "is signed by an issuer", "canonicalized ... reported interaction", and a section
  rename); and normalized "attested" to "reported" in the README.md protocol-boundary paragraph for accuracy.

Sentinels (frozen; unchanged)

receipt types 61, extension groups 19, conformance requirement IDs 290, conformance sections 32, API contract
keys 27, wire format 0.2, published packages 36, build targets 107. errors_version and SERVER_VERSION move
0.15.2 -> 0.15.3; no error definitions are added (only the version field changes in errors.json).

Not changed

No schema, registry, type URI, extension group, wire format, signing envelope, public API, exported symbol, CLI
command/flag, or package-set change. No tag, publish, GitHub release, or external action is performed by this PR.

Validation

• Full suite: 475 test files, 11863 tests, all passing (matches the stamped facts.json metrics).
• Conformance: 676 tests passing.
• format:check, git diff --check, typecheck:core, registries-schema validation, the semantic no-widening
  gate (18/18, "safe to tag"), the API-contract check (924 exports, 27 contract keys), codegen-drift, and
  forbid-strings all pass.
• verify-release: all release facts verified (25 passed, 0 failed; the only skip is the gate report generated
  at tag time).