Gates PUT /memories/config behind a startup-validated flag. Production
deploys get 410 Gone; dev/test environments opt in via env var and keep
v1 behavior. Follows the workspace rule "config is validated at startup,
routes don't re-check at request time" — no NODE_ENV branching in the
route handler.

- src/config.ts: add runtimeConfigMutationEnabled to RuntimeConfig,
  parsed from CORE_RUNTIME_CONFIG_MUTATION_ENABLED (default false).
  Added to SUPPORTED_RUNTIME_CONFIG_FIELDS so the partition test keeps
  it honest.
- src/app/runtime-container.ts: CoreRuntimeConfigRouteAdapter.current()
  now includes runtimeConfigMutationEnabled. Default adapter populates
  from config singleton at construction time — memoized, not a per-
  request env read.
- src/routes/memories.ts: RuntimeConfigRouteSnapshot gains the field.
  PUT /memories/config checks configRouteAdapter.current()
  .runtimeConfigMutationEnabled; false → 410 Gone with a message
  pointing at the env var. true → existing behavior preserved.
- .env.test.example: documents the flag with CORE_RUNTIME_CONFIG_MUTATION_ENABLED=true
  for test/dev. .env.test (gitignored) should be updated locally.
- .env.example: documents the flag as opt-in; left commented out so
  production deploys inherit the safe default.
- src/__tests__/memory-route-config-seam.test.ts: MutableRouteConfig
  gains the field (set true for existing tests); new test asserts PUT
  returns 410 when the flag is flipped to false.
- docs/consuming-core.md: new "PUT /memories/config — dev/test only"
  section explaining the gate and dev-mode setup.
- atomicmemory-research/docs/core-repo/readme/readme-migration-from-v1.md:
  §8 updated to reflect the deprecation path and point at the env var.

962/962 tests pass (961 + 1 new 410 test). tsc --noEmit clean.
fallow --no-cache 0 above threshold.

Parity audit (see v1-v2-functional-parity-audit.md §2) confirmed zero
production callers of PUT /memories/config, so the deprecation is
parity-preserving by definition.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Removes embeddingProvider, embeddingModel, llmProvider, llmModel from
updateRuntimeConfig() and rejects them at the HTTP boundary with 400.
This is a bug fix disguised as a deprecation: v1 accepted these fields
but the embedding.ts / llm.ts provider caches are stateful and fixed at
first use, so mid-flight mutation never actually took effect. Making
them explicitly startup-only aligns the API contract with reality.

Parity audit (v1-v2-functional-parity-audit.md §4) confirmed no caller
relies on runtime provider/model mutation — both in-repo tests and the
vendored prototype UI only mutated thresholds / maxSearchResults, which
remain mutable in dev/test mode.

- src/config.ts: narrow RuntimeConfigUpdates to 4 mutable fields
  (similarityThreshold, audnCandidateThreshold,
  clarificationConflictThreshold, maxSearchResults). Delete the four
  provider/model blocks from updateRuntimeConfig(). Remove the now-dead
  requireSupportedProvider and requireNonEmpty helpers.
- src/app/runtime-container.ts: narrow CoreRuntimeConfigRouteAdapter
  .update() signature to match.
- src/routes/memories.ts: narrow RuntimeConfigRouteUpdates; add
  STARTUP_ONLY_CONFIG_FIELDS = ['embedding_provider', 'embedding_model',
  'llm_provider', 'llm_model'] and reject the PUT with 400 if any
  appear in the body, with a message pointing at the env vars.
- src/__tests__/memory-route-config-seam.test.ts: new test asserts
  400 rejection with rejected: ['embedding_provider'].
- docs/consuming-core.md + migration doc: document the startup-only
  constraint with the rationale.

963/963 tests pass (962 + 1 new 400 test). tsc --noEmit clean.
fallow --no-cache 0 above threshold.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Codex review caught two drift points between the implementation and the
docs/response payload:

- docs/api-reference.md §PUT /memories/config still documented the pre-
  Step-3b/3c contract — provider/model mutation fields and "all fields
  optional". Rewrote the section to: flag dev/test-only gating, list the
  4 currently-mutable fields, document the 400/410 responses with
  example payloads, and explain the startup-only rationale.
- src/routes/memories.ts: the success-response `note` contradicted the
  handler's own behavior. "Provider/model changes are applied in-memory
  for local experimentation" is no longer true (those fields are rejected
  earlier in the same handler). Replaced with an honest note pointing
  threshold-only mutation at dev use and startup restart for provider/
  model.

963/963 tests pass. tsc --noEmit clean.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>