fix: add read-only Lody history extension [risk:medium]

[Leeeon233]

Risk: 🟡 medium | Confidence: high — adds a private request surface and history projection path; covered by transport, writer-conflict, full unit, typecheck, and build validation

Summary

• advertise agentCapabilities._meta.lody.readSessionHistory version 1 with method _lody/session/history/read
• read Codex history through thread/read with includeTurns: true
• project title and turns through standard ACP session/update notifications using ephemeral state
• keep loadSession and interactive session ownership unchanged

Why

Lody conversation import currently reaches Codex through loadSession, which resumes the thread before reading it. Codex rejects that resume when another process already owns the thread writer. The new Lody-only request provides a read-only path that never calls thread/resume or installs an active adapter session.

Verification

• npm run typecheck
• npm test — 463 passed, 29 skipped
• npm run build

Review focus

Please verify that the new path remains read-only: one thread/read, standard history notifications, and no active session-map installation.

Affected package: acp-extension-codex

Related: https://github.com/loro-dev/lody/issues/3440

The Lody caller migration will be handled separately after this extension lands.