chat: remove Pi runner — route all chat/pipeline/channels through Claude

Stage 1 of removing Pi (Claude-only). Cuts the non-Claude branches in the chat
WS handler, pipeline executor, and channel send-and-await; deletes the Pi
sidecar, its ecosystem entry, pi-bridge, and the Pi model-listing spawn (now a
static Claude tier list). Adds a guard coercing any legacy non-claude-code model
preference to the Claude default so old settings don't break chat or jobs.
Removes the dead no-op session-save REST route and stale Pi docs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/servers/api/pi/rest.ts

@@ -1,7 +1,6 @@
 import type { Context } from 'hono';
 import { createRouter } from '../../create-router';
 import * as storage from './storage';
-import { readLocalProviders } from '../server-settings/pi-mono';
 import { readSttConfig } from '../server-settings/stt';
 import { listPiModels } from './list-models';
 import { getHomeDirForRole } from '../../data-path';
@@ -12,19 +11,12 @@ import { getUserSettings } from 'officerdb';
 export const piRestRouter = createRouter();
 
 /**
- * GET /api/pi/models
+ * GET /api/pi/models — Claude tiers only.
  */
 piRestRouter.get('/pi/models', async (ctx: Context) => {
   try {
     const models = await listPiModels();
-
     const providerNames: Record<string, string> = { 'claude-code': 'Claude Code' };
-    const localProviders = await readLocalProviders();
-    for (const lp of localProviders) {
-      providerNames[`officer-local-${lp.id}`] = lp.name;
-    }
-
-    logger.info('Models endpoint', { count: models.length, providers: [...new Set(models.map((m) => m.provider))] });
     return ctx.json({ models, providerNames, hostHome: process.env.HOME ?? '' });
   } catch (err) {
     logger.error('Failed to list models', { error: String(err) });
@@ -57,14 +49,6 @@ piRestRouter.get('/pi/sessions/:sessionId', async (ctx: Context) => {
   }
 });
 
-/**
- * PUT /api/pi/sessions/:sessionId/messages
- * No-op — sessions are persisted server-side via WebSocket events
- */
-piRestRouter.put('/pi/sessions/:sessionId/messages', async (ctx: Context) => {
-  return ctx.json({ success: true });
-});
-
 /**
  * POST /api/pi/stt
  */