Update `packages/lal/LAL-ARCHITECTURE.md` for the pi-agent-core harness and inbox loops

[0xpatrickbot]

Problem

packages/lal/LAL-ARCHITECTURE.md has a short post-pi-harness note, but the body still describes the pre-pi implementation. It incorrectly presents lal as a monolithic agent with approximately 1,507 lines, 16 hardcoded OpenAI-format tool schemas, a single switch dispatcher, no dynamic context building, and an active provider abstraction.

The documentation should be updated to match the implementation on origin/llm. This is a documentation update, not a request to rewrite lal or redesign its runtime.

Current model to document

lal runs its agent loop on @earendil-works/pi-agent-core through @endo/agentry/harness via makePiAgent.

The inbox integration has two layers, coupled by a trigger prompt and mail tools:

┌─ OUTER: inbox follow-loop  (inbox-loop.js) ────────────────────────┐
│  iterateReader(E(powers).followMessages())   ← @endo/exo-stream    │
│  • races next() vs. cancellation                                   │
│  • skips own messages; defers partial (done:false); skips          │
│    already-seen-then-edited numbers (editMessage)                  │
│  • per settled inbound msg →  runOneRound("You have new mail…")    │
│                                     │                              │
│        ┌─ INNER: one pi round  (round-runner.js → agent-round.js) ─┐│
│        │  for await (event of runAgentRound(piAgent, prompt))      ││
│        │    ToolCallStart / ToolCallEnd / Message / Error          ││
│        │  PiAgent tool surface: mail tools + execute code-mode …   ││
│        │    listMessages / send / reply / dismiss / editMessage    ││
│        │      →  E(powers).*   (back into the daemon inbox)        ││
│        └────────────────────────────────────────────────────────────┘│
└────────────────────────────────────────────────────────────────────┘

The revised document should explain that:

• The worker builds a listTools/execTool surface at spawn time. It is not a static OpenAI schema array dispatched by one switch.
• Pi provides the agent loop, but has no native inbox concept. The outer Endo follow loop supplies inbound events, while mail tools target E(powers).*.
• runRound consumes runAgentRound events including tool-call starts, tool-call ends, messages, and errors.
• lal already supports the send/act/edit message model, including editMessage, done: false partials, messageHistory, and seenInboundNumbers.
• packages/lal/providers/ is a compatibility surface for downstream consumers, not the provider architecture used by lal’s worker loop.

Acceptance criteria

• Remove or replace the remaining pre-pi descriptions throughout LAL-ARCHITECTURE.md.
• Describe the responsibilities of inbox-loop.js, round-runner.js, agent-round.js, agent.js, and tools/mail.js.
• Preserve the two-layer diagram above in the revised document.
• Clearly distinguish the pi agent runtime from Endo’s inbox and capability surfaces.
• Keep the scope limited to bringing the architecture documentation up to date.