Enforce 100% per-file test coverage on packages/*/src

vitest coverage (v8 provider) with per-file 100% thresholds for
statements, branches, functions, and lines. Scope: our runtime source
only — types-only files, vendor/ (upstream code), and examples/
(exercised by the demo smoke test) are excluded. yarn test:coverage
runs the gate.

59 tests added to close every gap: llm generate-waterfall and adapter
disposal; assembler edge protocol (duplicate block-start, stragglers
after block-end, id fallback, usage omission, invariant violation);
the whole Inbox surface incl. the wakeup-overwrite race; LoopAgent
disposed-state throws and double-stop idempotence; config-driven agent
creation; loop backstop catches (throwing turn-start/turn-end
listeners, non-Error throws, non-JSON tool arguments); system-prompt
dynamic sections and disposer paths; tools errorMessage fallbacks and
the full schema-DSL emission matrix. Genuinely unreachable defensive
guards carry /* v8 ignore */ comments with stated reasons rather than
deletion (132 tests total).

packages/agent-loop/tests/loop.spec.ts

@@ -383,6 +383,30 @@ describe('agent loop', () => {
     expect(() => { send(agent, 'too late') }).toThrow('disposed')
   })
 
+  it('creates agents from config on startup', async () => {
+    const adapter = new MockAdapter([textResponse('from config')])
+    const ctx = new Context()
+    await ctx.plugin(LlmService)
+    await ctx.plugin(SessionStore)
+    await ctx.plugin(SystemPrompt)
+    await ctx.plugin(ToolRegistry)
+    await ctx.plugin(AgentRegistry)
+    await ctx.plugin(AgentLoop, {
+      agents: [{ id: 'config-agent', model: 'mock', systemPrompt: 'Config prompt' }],
+    })
+    ctx.llm.registerAdapter(['mock'], adapter)
+
+    const agent = ctx.agents.get('config-agent')! as LoopAgent
+    expect(agent).toBeDefined()
+    expect(agent.id).toBe('config-agent')
+    expect(agent.options.model).toBe('mock')
+
+    // the agent is alive: send triggers a turn
+    send(agent, 'hi')
+    await waitForIdle(ctx, agent)
+    expect(adapter.requests).toHaveLength(1)
+  })
+
   it('replays a session log into an identical derived history', async () => {
     const adapter = new MockAdapter([
       toolCallResponse('c1', 'echo', { text: 'x' }),