feat: Phase 3 V1 — Auto-Organization (domain_tags + valid_until)

Adds structural metadata that the LLM triage was already implicitly
reasoning about ("stale snapshot" → reject). Phase 3 captures that
reasoning as fields so it can DRIVE retrieval, not just rejection.

Schema (src/atocore/models/database.py):
- domain_tags TEXT DEFAULT '[]'  JSON array of lowercase topic keywords
- valid_until DATETIME            ISO date; null = permanent
- idx_memories_valid_until index for efficient expiry queries

Memory service (src/atocore/memory/service.py):
- Memory dataclass gains domain_tags + valid_until
- create_memory, update_memory accept/persist both
- _row_to_memory safely reads both (JSON-decode + null handling)
- _normalize_tags helper: lowercase, dedup, strip, cap at 10
- get_memories_for_context filters expired (valid_until < today UTC)
- _rank_memories_for_query adds tag-boost: memories whose domain_tags
  appear as substrings in query text rank higher (tertiary key after
  content-overlap density + absolute overlap, before confidence)

LLM extractor (_llm_prompt.py → llm-0.5.0):
- SYSTEM_PROMPT documents domain_tags (2-5 keywords) + valid_until
  (time-bounded facts get expiry dates; durable facts stay null)
- normalize_candidate_item parses both fields from model output with
  graceful fallback for string/null/missing

LLM triage (scripts/auto_triage.py):
- TRIAGE_SYSTEM_PROMPT documents same two fields
- parse_verdict extracts them from verdict JSON
- On promote: PUT /memory/{id} with tags + valid_until BEFORE
  POST /memory/{id}/promote, so active memories carry them

API (src/atocore/api/routes.py):
- MemoryCreateRequest: adds domain_tags, valid_until
- MemoryUpdateRequest: adds domain_tags, valid_until, memory_type
- GET /memory response exposes domain_tags + valid_until + created_at

Triage UI (src/atocore/engineering/triage_ui.py):
- Renders existing tags as colored badges
- Adds inline text field for tags (comma-separated) + date picker for
  valid_until on every candidate card
- Save&Promote button persists edits via PUT then promotes
- Plain Promote (and Y shortcut) also saves tags/expiry if edited

Wiki (src/atocore/engineering/wiki.py):
- Search now matches memory content OR domain_tags
- Search results render tags as clickable badges linking to
  /wiki/search?q=<tag> for cross-project navigation
- valid_until shown as amber "valid until YYYY-MM-DD" hint

Tests: 303 → 308 (5 new for Phase 3 behavior):
- test_create_memory_with_tags_and_valid_until
- test_create_memory_normalizes_tags
- test_update_memory_sets_tags_and_valid_until
- test_get_memories_for_context_excludes_expired
- test_context_builder_tag_boost_orders_results

Deferred (explicitly): temporal_scope enum, source_refs memory graph,
HDBSCAN clustering, memory detail wiki page, backfill of existing
actives. See docs/MASTER-BRAIN-PLAN.md.

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

src/atocore/api/routes.py

@@ -254,12 +254,17 @@ class MemoryCreateRequest(BaseModel):
     project: str = ""
     confidence: float = 1.0
     status: str = "active"
+    domain_tags: list[str] | None = None
+    valid_until: str = ""
 
 
 class MemoryUpdateRequest(BaseModel):
     content: str | None = None
     confidence: float | None = None
     status: str | None = None
+    memory_type: str | None = None
+    domain_tags: list[str] | None = None
+    valid_until: str | None = None
 
 
 class ProjectStateSetRequest(BaseModel):
@@ -458,6 +463,8 @@ def api_create_memory(req: MemoryCreateRequest) -> dict:
             project=req.project,
             confidence=req.confidence,
             status=req.status,
+            domain_tags=req.domain_tags or [],
+            valid_until=req.valid_until or "",
         )
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))
@@ -502,6 +509,9 @@ def api_get_memories(
                 "reference_count": m.reference_count,
                 "last_referenced_at": m.last_referenced_at,
                 "updated_at": m.updated_at,
+                "created_at": m.created_at,
+                "domain_tags": m.domain_tags or [],
+                "valid_until": m.valid_until or "",
             }
             for m in memories
         ],
@@ -519,6 +529,9 @@ def api_update_memory(memory_id: str, req: MemoryUpdateRequest) -> dict:
             content=req.content,
             confidence=req.confidence,
             status=req.status,
+            memory_type=req.memory_type,
+            domain_tags=req.domain_tags,
+            valid_until=req.valid_until,
         )
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))