v1.13.1-B: read-path flip from tool_calls/tool_results JSON columns to message_parts

- schema.sql: new messages_with_parts view. tool_calls aggregates parts
  with kind='tool_call' as a jsonb array of {id, name, args}; tool_results
  picks the single sequence=0 part with kind='tool_result' as a jsonb
  {tool_call_id, output, truncated, error?}. COALESCE against the legacy
  jsonb columns means pre-v1.13.0 history (no parts rows) still reads
  correctly via the fallback, and fresh inserts (where parts dual-write
  follows the row INSERT) hit the legacy columns until the parts land.
- reasoning_parts column added to the view but not selected by any caller
  yet — v1.13.1-C extends the Message type and pulls it into the model
  payload alongside the type extension.
- Read sites switched to FROM messages_with_parts:
  - routes/chats.ts:427 (chat history GET)
  - routes/messages.ts:95 (session history GET)
  - routes/ws.ts:27 (WS snapshot on session connect, resume path)
  - services/inference/payload.ts (loadContext for model assembly)
  - services/compaction.ts (compaction's payload assembly)
- chats.ts:394 (discard_stale UPDATE RETURNING) unchanged — UPDATEs target
  messages directly and the returned shape is for a freshly-modified row
  where the legacy column is dual-written and correct.
- messages.ts:478/549 (ask_user_input correlation) intentionally not
  migrated — those query a different shape, ported in v1.13.1-C.
- Writes still target `messages` directly; the view is read-only.

Smoke verified against the live container:
- Equivalence: 5/5 messages with both legacy column and parts row return
  identical tool_calls jsonb between FROM messages and FROM messages_with_parts.
- Perf: EXPLAIN ANALYZE on the 42-message stress chat returns in ~1ms
  (50ms threshold). Bitmap Index Scan on message_parts_msg_seq_idx
  carries the parts lookups.
- API contract: GET /api/chats/:id/messages returns identical
  {id, name, args} tool_calls and {tool_call_id, output, truncated, error}
  tool_results shapes to frontend consumers — no UI changes needed.
- Inference path: sent a view_file prompt; assistant turn 1 emitted the
  tool_call, tool message captured the result, follow-up assistant turn
  read the result back via loadContext (now view-backed) and answered
  correctly. End-to-end loop intact.

v1.13.2 drops the dual-write + the JSON columns + simplifies the view
to just SELECT FROM message_parts.

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

apps/server/src/schema.sql

@@ -49,6 +49,42 @@ CREATE TABLE IF NOT EXISTS message_parts (
 );
 CREATE INDEX IF NOT EXISTS message_parts_msg_seq_idx ON message_parts (message_id, sequence);
 
+-- v1.13.1-B: read-path view. Read sites SELECT FROM messages_with_parts
+-- instead of messages so tool_calls / tool_results / reasoning_parts come
+-- from the granular message_parts table. The COALESCE means pre-v1.13.0
+-- history (no parts rows) still resolves via the legacy JSON columns; the
+-- dual-write from v1.13.0 keeps both in sync for all rows written since.
+-- Writes continue to target `messages` directly — the view is read-only.
+-- Shapes match the in-memory ToolCall / ToolResult types: tool_calls is a
+-- jsonb array of {id, name, args}, tool_results is a single jsonb object
+-- {tool_call_id, output, truncated, error?}. reasoning_parts is new — only
+-- consumed by the inference history fetch (payload.ts) so v1.13.1-C can
+-- wire reasoning into the model payload. Not surfaced in external APIs yet.
+CREATE OR REPLACE VIEW messages_with_parts AS
+SELECT
+  m.id, m.session_id, m.chat_id, m.role, m.content, m.kind, m.status,
+  m.last_seq, m.tokens_used, m.ctx_used, m.ctx_max,
+  m.started_at, m.finished_at, m.created_at, m.metadata,
+  m.summary, m.tail_start_id, m.compacted_at,
+  COALESCE(
+    (SELECT jsonb_agg(p.payload ORDER BY p.sequence)
+       FROM message_parts p
+      WHERE p.message_id = m.id AND p.kind = 'tool_call'),
+    m.tool_calls
+  ) AS tool_calls,
+  COALESCE(
+    (SELECT p.payload
+       FROM message_parts p
+      WHERE p.message_id = m.id AND p.kind = 'tool_result'
+      ORDER BY p.sequence
+      LIMIT 1),
+    m.tool_results
+  ) AS tool_results,
+  (SELECT jsonb_agg(p.payload ORDER BY p.sequence)
+     FROM message_parts p
+    WHERE p.message_id = m.id AND p.kind = 'reasoning') AS reasoning_parts
+FROM messages m;
+
 ALTER TABLE messages ADD COLUMN IF NOT EXISTS tokens_used INTEGER;
 ALTER TABLE messages ADD COLUMN IF NOT EXISTS ctx_used INTEGER;
 ALTER TABLE messages ADD COLUMN IF NOT EXISTS ctx_max INTEGER;