chore: snapshot working tree - pty_exited notifications + in-flight inference WIP

feat(booterm): structured pty_exited WS notifications. Plan-validated, impl-validated, code-reviewed green (contracts build clean, contracts test 29/29, booterm + web typecheck clean).

wip: in-progress inference/provider refactor (agents.ts, provider.ts, new llama-providers.ts, removed llama-args-validator), plus arena, dispatcher, compaction, schema changes.

openspec: pty-exit-notifications complete; x-agent-flags planned (not yet implemented).

apps/coder/src/services/__tests__/pi-config-sync.test.ts

@@ -0,0 +1,61 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { writeFileSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { buildPiProviderEntry } from '../pi-config-sync.js';
+import { loadLlamaProviders } from '../llama-providers.js';
+
+describe('buildPiProviderEntry', () => {
+  const fetchMock = vi.fn();
+
+  beforeEach(() => {
+    vi.stubGlobal('fetch', fetchMock);
+    fetchMock.mockResolvedValue(
+      new Response(JSON.stringify({ data: [{ id: 'qwen3.6-35b' }] }), {
+        status: 200,
+        headers: { 'content-type': 'application/json' },
+      }),
+    );
+    const file = {
+      defaultProvider: 'sam-desktop',
+      providers: [
+        { id: 'sam-desktop', label: 'Sam Desktop', baseUrl: 'http://a.test:8401', kind: 'llama-swap' },
+      ],
+    };
+    const path = join(tmpdir(), `llama-providers-pi-${Math.random().toString(36).slice(2)}.json`);
+    writeFileSync(path, JSON.stringify(file), 'utf8');
+    loadLlamaProviders(path, 'http://legacy.test:8080');
+  });
+
+  afterEach(() => {
+    vi.unstubAllGlobals();
+  });
+
+  it('emits a Pi-routable provider with gateway baseUrl and composite model ids', async () => {
+    const entry = await buildPiProviderEntry('http://127.0.0.1:9502');
+    expect(entry.baseUrl).toBe('http://127.0.0.1:9502/v1');
+    expect(entry.api).toBe('openai-completions');
+    expect(entry.models?.map((m) => m.id)).toEqual(['sam-desktop/qwen3.6-35b']);
+    expect(entry.models?.[0]?.contextWindow).toBeGreaterThan(0);
+    expect(entry.models?.[0]?.cost).toEqual({ input: 0, output: 0, cacheRead: 0, cacheWrite: 0 });
+  });
+
+  it('preserves hand-tuned per-model overrides on re-sync', async () => {
+    const existing = {
+      baseUrl: 'http://stale:1/v1',
+      models: [
+        {
+          id: 'sam-desktop/qwen3.6-35b',
+          name: 'Old Name',
+          contextWindow: 262_144,
+          maxTokens: 65_536,
+        },
+      ],
+    };
+    const entry = await buildPiProviderEntry('http://127.0.0.1:9502', existing);
+    expect(entry.baseUrl).toBe('http://127.0.0.1:9502/v1'); // ours wins
+    const m = entry.models?.[0];
+    expect(m?.contextWindow).toBe(262_144); // hand-tuned values preserved
+    expect(m?.maxTokens).toBe(65_536);
+  });
+});