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/engineering/wiki.py

@@ -211,15 +211,32 @@ def render_search(query: str) -> str:
             )
         lines.append('</ul>')
 
-    # Search memories
+    # Search memories — match on content OR domain_tags (Phase 3)
     all_memories = get_memories(active_only=True, limit=200)
     query_lower = query.lower()
-    matching_mems = [m for m in all_memories if query_lower in m.content.lower()][:10]
+    matching_mems = [
+        m for m in all_memories
+        if query_lower in m.content.lower()
+        or any(query_lower in (t or "").lower() for t in (m.domain_tags or []))
+    ][:20]
     if matching_mems:
         lines.append(f'<h2>Memories ({len(matching_mems)})</h2><ul>')
         for m in matching_mems:
             proj = f' <span class="tag">{m.project}</span>' if m.project else ''
-            lines.append(f'<li>[{m.memory_type}]{proj} {m.content[:200]}</li>')
+            tags_html = ""
+            if m.domain_tags:
+                tag_links = " ".join(
+                    f'<a href="/wiki/search?q={t}" class="tag-badge">{t}</a>'
+                    for t in m.domain_tags[:5]
+                )
+                tags_html = f' <span class="mem-tags">{tag_links}</span>'
+            expiry_html = ""
+            if m.valid_until:
+                expiry_html = f' <span class="mem-expiry">valid until {m.valid_until[:10]}</span>'
+            lines.append(
+                f'<li>[{m.memory_type}]{proj}{tags_html}{expiry_html} '
+                f'{m.content[:200]}</li>'
+            )
         lines.append('</ul>')
 
     if not entities and not matching_mems:
@@ -302,6 +319,11 @@ _TEMPLATE = """<!DOCTYPE html>
   .triage-notice { background: var(--card); border-left: 4px solid var(--accent); padding: 0.6rem 1rem; border-radius: 4px; margin: 0.8rem 0; }
   .triage-warning { background: #fef3c7; color: #78350f; border-left: 4px solid #d97706; padding: 0.6rem 1rem; border-radius: 4px; margin: 0.8rem 0; }
   @media (prefers-color-scheme: dark) { .triage-warning { background: #451a03; color: #fde68a; } }
+  .mem-tags { display: inline-flex; gap: 0.25rem; flex-wrap: wrap; vertical-align: middle; }
+  .tag-badge { background: var(--accent); color: white; padding: 0.1rem 0.5rem; border-radius: 10px; font-size: 0.7rem; font-family: monospace; text-decoration: none; font-weight: 500; }
+  .tag-badge:hover { opacity: 0.85; text-decoration: none; }
+  .mem-expiry { font-size: 0.75rem; color: #d97706; font-style: italic; margin-left: 0.4rem; }
+  @media (prefers-color-scheme: dark) { .mem-expiry { color: #fbbf24; } }
 </style>
 </head>
 <body>