feat: v2.0.4 "Deep Reference" — cognitive reasoning engine + 10 bug fixes

New features:
- deep_reference tool (#22): 8-stage cognitive reasoning pipeline with FSRS-6
  trust scoring, intent classification (FactCheck/Timeline/RootCause/Comparison/
  Synthesis), spreading activation expansion, temporal supersession, trust-weighted
  contradiction analysis, relation assessment, dream insight integration, and
  algorithmic reasoning chain generation — all without calling an LLM
- cross_reference (#23): backward-compatible alias for deep_reference
- retrieval_mode parameter on search (precise/balanced/exhaustive)
- get_batch action on memory tool (up to 20 IDs per call)
- Token budget raised from 10K to 100K on search + session_context
- Dates (createdAt/updatedAt) on all search results and session_context lines

Bug fixes (GitHub Issue #25 — all 10 resolved):
- state_transitions empty: wired record_memory_access into strengthen_batch
- chain/bridges no storage fallback: added with edge deduplication
- knowledge_edges dead schema: documented as deprecated
- insights not persisted from dream: wired save_insight after generation
- find_duplicates threshold dropped: serde alias fix
- search min_retention ignored: serde aliases for snake_case params
- intention time triggers null: removed dead trigger_at embedding
- changelog missing dreams: added get_dream_history + event integration
- phantom Related IDs: clarified message text
- fsrs_cards empty: documented as harmless dead schema

Security hardening:
- HTTP transport CORS: permissive() → localhost-only
- Auth token panic guard: &token[..8] → safe min(8) slice
- UTF-8 boundary fix: floor_char_boundary on content truncation
- All unwrap() removed from HTTP transport (unwrap_or_else fallback)
- Dream memory_count capped at 500 (prevents O(N²) hang)
- Dormant state threshold aligned (0.3 → 0.4)

Stats: 23 tools, 758 tests, 0 failures, 0 warnings, 0 unwraps in production

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CONTRIBUTING.md

@@ -26,7 +26,7 @@ vestige/
 
 ### Prerequisites
 
-- **Rust** (1.85+ stable): [rustup.rs](https://rustup.rs)
+- **Rust** (1.91+ stable): [rustup.rs](https://rustup.rs)
 - **Node.js** (v22+): [nodejs.org](https://nodejs.org)
 - **pnpm** (v9+): `npm install -g pnpm`
 
@@ -56,7 +56,7 @@ VESTIGE_TEST_MOCK_EMBEDDINGS=1 cargo test --workspace
 ## Running Tests
 
 ```bash
-# All tests (734 total)
+# All tests (746+ total)
 VESTIGE_TEST_MOCK_EMBEDDINGS=1 cargo test --workspace
 
 # Core library tests only (352 tests)
@@ -137,7 +137,7 @@ The MCP server and dashboard. Key modules:
 |--------|---------|
 | `server.rs` | MCP JSON-RPC server (rmcp 0.14) |
 | `cognitive.rs` | CognitiveEngine — 29 stateful modules |
-| `tools/` | One file per MCP tool (21 tools) |
+| `tools/` | One file per MCP tool (23 tools) |
 | `dashboard/` | Axum HTTP + WebSocket + event bus |
 
 ### apps/dashboard