refactor: codebase audit cleanup — dead code, dedup, module splits

Multi-agent audit + aggressive cleanup across server/web/coder/booterm,
delivered behind a DEFER discipline so none of the in-flight files were
touched. Removes dead code/deps/columns, dedups server + coder helpers,
and splits the oversized modules (tools.ts, opencode-server.ts,
sentinel-summaries, turn.ts, TerminalPane.tsx) behind stable contracts.
Adds 78 parity/unit tests (server 587, coder 323); fixes two latent bugs
(ChatPane queue keys, FileViewerOverlay blank-line parity).

Intended tag: v2.7.12-audit-cleanup.

apps/server/src/services/inference/payload.ts

@@ -10,7 +10,8 @@ import * as compaction from '../compaction.js';
 import { buildSystemPromptWithFingerprint } from '../system-prompt.js';
 import { isAnySentinel } from './sentinels.js';
 import { PRUNE_TRIGGER_TOKENS, prune } from './prune.js';
-import type { InferenceContext } from './turn.js';
+import type { InferenceContext } from './types.js';
+import { INFERENCE_MESSAGE_COLUMNS } from '../message-columns.js';
 
 export interface OpenAiMessage {
   role: 'system' | 'user' | 'assistant' | 'tool';
@@ -205,9 +206,7 @@ export async function loadContext(
   // v1.13.1-C: also pull reasoning_parts so assistant messages from
   // reasoning models can be replayed with their reasoning context preserved.
   const history = await sql<Message[]>`
-    SELECT id, session_id, chat_id, role, content, kind, tool_calls, tool_results, status, last_seq,
-           tokens_used, ctx_used, ctx_max, started_at, finished_at, created_at, metadata,
-           reasoning_parts
+    SELECT ${sql.unsafe(INFERENCE_MESSAGE_COLUMNS)}
     FROM messages_with_parts
     WHERE chat_id = ${chatId} AND compacted_at IS NULL
     ORDER BY created_at ASC, id ASC