enhance(#1964): semantic knowledge-base recall via MemPalace (keyword fallback) (#2416)

* test(#1964): add failing-first semantic-recall contract tests

Epic #1957 Phase 3C (final). Source-text-is-the-product contract tests:
semantic recall via MemPalace (top-k meaning-similar prior resolutions, catches
same-root-cause/different-wording cases), indexing resolved sessions at archive,
graceful degradation to keyword matching when MemPalace is absent,
knowledge-base.md stays the durable plain-text source of truth, agent Phase 0 /
Matching Logic is semantic-first (the stale 'keyword overlap, not semantic
similarity' claim must go), and no new embedding/vector infra (reuse MemPalace).

Failing-first: reference, the Matching Logic reframe, the Phase 0 consolidation,
and the archive indexing step do not yet exist.

* feat(#1964): semantic knowledge-base recall via MemPalace (keyword fallback)

Epic #1957 Phase 3C (FINAL). Replaces keyword-overlap matching with semantic
recall: at Phase 0 the debugger queries MemPalace with the current symptoms
and surfaces the top-k meaning-similar prior resolutions, catching the
same-root-cause/different-wording cases keyword overlap missed (the self-noted
'keyword overlap, not semantic similarity' limitation). Resolved sessions are
indexed into MemPalace at archive (symptoms + root_cause(s) + fix + recurrence
guard). knowledge-base.md remains the durable plain-text source of truth; when
MemPalace is absent the debugger falls back to keyword-overlap matching
(logged, never a silent skip). No new embedding/vector infrastructure —
MemPalace is reused.

Size-neutral agent edits: the Matching Logic section reframed (keyword-only ->
semantic-first + keyword-fallback + @-include); Phase 0's three keyword bullets
consolidated into one semantic-first bullet; one MemPalace-indexing step added
at archive. Agent at 57222 B (122 B headroom — final phase). Full rules in
gsd-core/references/debugger-semantic-recall.md. INVENTORY + manifest +
agent-size baseline + install-parity goldens + AGENTS.md updated.

* fix(#1964): address orthogonal review (invocation mechanism, index Resolution-not-symptoms + redaction, fallback detail)

- HIGH: the 'query MemPalace' instruction was WHAT-level only; the agent has
  no MCP tools. Added an Invocation section naming the Bash CLI
  (mempalace search --wing <wing>) + MCP-when-registered + wing resolution
  (config.mempalace.wing -> project_code -> project dir), matching every other
  MemPalace integration. Without this the feature silently degraded to keyword
  matching even when MemPalace was present.
- MEDIUM (security x2): index the agent-authored Resolution summary
  (root_cause + fix + recurrence_guard), NOT raw user-supplied Symptoms —
  excludes attacker-controlled prose from the cross-session index AND reduces
  secret/PII leakage. Redact secret-shaped values before indexing. Stated the
  write order (KB append + commit MUST succeed before indexing).
- LOW: restored 'identifiers' + 'case-insensitive' to the keyword fallback;
  added a test asserting the fallback mechanics survived the Phase 0
  consolidation (Error patterns field, 2+ token overlap, identifiers,
  case-insensitive).

* chore(#1964): ratchet agent-size baseline downward (leaner archive bullet shrank gsd-debugger.md 57222->57197)

* chore(#1964): backfill changeset pr number (PR #2416)

docs/AGENTS.md

@@ -406,6 +406,7 @@ runs its default whole-repo scan.
 - Classifies each failure as Bohrbug / Heisenbug-Mandelbug / Concurrency at Phase 1.75 and routes the investigation technique accordingly (routes Bohrbugs to SBFL+bisect, Heisenbugs to record-replay/stability with SBFL skipped, Concurrency to the atomicity/order/deadlock checklist)
 - Hardens regression tests via PBT shrinking (minimized counterexample as the seed), explicit oracle classification (specified/derived/metamorphic/implicit), and boundary neighbors around the fixed equivalence class
 - Emits a blameless-postmortem Prevention block at resolution (branching 5-Whys, why-wasn't-this-caught, a concrete recurrence guard) and records `why_not_caught` + `recurrence_guard` in the knowledge base so the same bug class is prevented, not just fixed
+- Recalls prior resolved sessions semantically via MemPalace at Phase 0 (top-k meaning-similar), catching same-root-cause/different-wording cases keyword overlap misses; falls back to keyword matching when MemPalace is absent
 - Appends to persistent knowledge base on resolution
 - Consults knowledge base on new sessions
 

docs/INVENTORY-MANIFEST.json

@@ -221,6 +221,7 @@
       "debugger-rca-branching.md",
       "debugger-repro-hardening.md",
       "debugger-sbfl.md",
+      "debugger-semantic-recall.md",
       "decimal-phase-calculation.md",
       "doc-conflict-engine.md",
       "domain-probes.md",

docs/INVENTORY.md

@@ -300,6 +300,7 @@ Full roster at `gsd-core/references/*.md`. References are shared knowledge docum
 | `debugger-bug-taxonomy.md` | Bug-taxonomy classification (Bohrbug/Heisenbug/Concurrency) + technique routing table loaded by `gsd-debugger`. |
 | `debugger-repro-hardening.md` | Regression-test hardening (PBT shrinking + oracle classification + boundary neighbors) loaded by `gsd-debugger`. |
 | `debugger-prevention.md` | Prevention / blameless-postmortem output (5-Whys + why-not-caught + recurrence guard) loaded by `gsd-debugger`. |
+| `debugger-semantic-recall.md` | Semantic knowledge-base recall via MemPalace (keyword-fallback) loaded by `gsd-debugger`. |
 | `mandatory-initial-read.md` | Shared required-reading boilerplate injected into agent prompts. |
 | `agent-skills-bootstrap.md` | Shared agent_skills self-load contract (query + Read + dedup guard) injected into all 22 consumer agents. |
 | `project-skills-discovery.md` | Shared project-skills-discovery boilerplate injected into agent prompts. |