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.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/server/src/services/synthesisPipeline.ts

@@ -24,12 +24,12 @@ import { TOOLS_BY_NAME } from './tools.js';
 import { streamCompletion } from './inference/stream-phase.js';
 import { SYNTHESIS_SYSTEM_PROMPT } from './synthesisPrompt.js';
 import { insertParts } from './inference/parts.js';
-import * as modelContext from './model-context.js';
+import { finalizeStreamedRow } from './inference/error-handler.js';
 import { readTruncation } from './truncate.js';
 
 import type { Session } from '../types/api.js';
 import type { OpenAiMessage } from './inference/payload.js';
-import type { InferenceContext, TurnArgs } from './inference/turn.js';
+import type { InferenceContext, TurnArgs } from './inference/types.js';
 
 export const SYNTHESIS_TOOLS: ReadonlySet<string> = new Set([
   'get_codebase_overview',
@@ -192,44 +192,28 @@ export async function runSynthesisPass(p: SynthesisParams): Promise<boolean> {
       combinedSignal,
     );
 
-    const mctx = await modelContext.getModelContext(p.session.model);
-    const nCtx = mctx?.n_ctx ?? null;
-    const [updated] = await p.ctx.sql<
-      {
-        tokens_used: number | null;
-        ctx_used: number | null;
-        ctx_max: number | null;
-        finished_at: string | null;
-      }[]
-    >`
-      UPDATE messages
-      SET content = ${streamResult.content},
-          status = 'complete',
-          tokens_used = ${streamResult.completionTokens},
-          ctx_used = ${streamResult.promptTokens},
-          ctx_max = ${nCtx},
-          finished_at = clock_timestamp()
-      WHERE id = ${synthMessageId}
-      RETURNING tokens_used, ctx_used, ctx_max, finished_at
-    `;
-    await insertParts(p.ctx.sql, [
-      {
-        message_id: synthMessageId,
-        sequence: 0,
-        kind: 'synthesis',
-        payload: { text: streamResult.content },
-      },
-    ]);
-    p.ctx.publish(p.args.sessionId, {
-      type: 'message_complete',
-      message_id: synthMessageId,
-      chat_id: p.args.chatId,
-      tokens_used: updated?.tokens_used ?? null,
-      ctx_used: updated?.ctx_used ?? null,
-      ctx_max: updated?.ctx_max ?? null,
-      started_at: startedAt,
-      finished_at: updated?.finished_at ?? null,
+    // P5: the n_ctx lookup + complete UPDATE + message_complete frame are the
+    // shared success-finalize atom (finalizeStreamedRow). beforeComplete writes
+    // the kind='synthesis' part in the original order (UPDATE → insertParts →
+    // message_complete), preserving timing exactly.
+    await finalizeStreamedRow(p.ctx, {
+      sessionId: p.args.sessionId,
+      chatId: p.args.chatId,
+      messageId: synthMessageId,
       model: p.session.model,
+      content: streamResult.content,
+      completionTokens: streamResult.completionTokens,
+      promptTokens: streamResult.promptTokens,
+      startedAt,
+      beforeComplete: () =>
+        insertParts(p.ctx.sql, [
+          {
+            message_id: synthMessageId!,
+            sequence: 0,
+            kind: 'synthesis',
+            payload: { text: streamResult.content },
+          },
+        ]),
     });
     p.ctx.publishUser({
       type: 'chat_status',