test: 会话事件写入侧防护回归测试 (refs #8)

[spacexun2]

Note: re-opening the original PR #12

This PR re-submits the original [#12]. It was auto-closed by GitHub with "head repository deleted" on 2026-09-04 when the author's head fork (spacexun2/dsh-agent-teams) was deleted by accident — not a rejection on the merits. The fork has been rebuilt and the branch is replayed on top of the current main (426024f).

What it does

An offline regression test for the session event write-guard from issue #8, plus a standalone pnpm verify:events entry:

• scripts/verify-events.mjs: drives the built lib/events.js against a stubbed @deepseek-ai/dsh-session and pins four behaviors: (1) agent-teams/* event types the harness does not recognize are never written to the session log; (2) recognized first-party types (e.g. tool-workflow/run-started) are written as usual; (3) a throwing session.append is contained inside appendTeamEvent; (4) the captainSessionOf fallback semantics (offline captain falls back to the caller session; a live captain session wins).
• scripts/mock-dsh-session-loader.mjs: an ESM loader stub that pins the issue session.append 写入不可忽略的自定义事件类型，导致历史会话拒读（SessionFormatUnsupportedError） #8 scenario deterministically (a harness that only knows first-party tool-workflow/* / agent/* vocabulary), so the test does not drift with the locally installed harness version.
• package.json: adds "verify:events": "node scripts/verify-events.mjs". As decided earlier, it stays out of the aggregate verify gate; the rest of the chain is untouched.

Fit to the current write path (post-alpha.2)

The original PR targeted the 0.1.10-era write path. After the alpha.2 refactor (bf50b49 and follow-ups) the guard contract is intact: appendTeamEvent in src/events.ts still decides write/skip by the harness KNOWN_SESSION_EVENT_TYPES, still wraps session.append in try/catch, and captainSessionOf keeps its signature and fallback semantics. The conversationEvents → uiConversation rename happened on the client side and does not touch this test surface. Adaptation in this replay: the event vocabulary now covers the 10 agent-teams/* types in the current src/event-types.ts (including the newer team-halted, team-resumed, plan-discarded), with the stub comments updated; since rc.1 the @deepseek-ai/* packages are installed as devDependencies and the stub is kept anyway to pin the scenario.

Local verification (current main + this branch, Windows / Node v24.16.0)

pnpm build (clean-build.mjs && tsc -p tsconfig.json && tsc -p tsconfig.client.json && tsdown) → ok
node scripts/verify-events.mjs
  1/4 out-of-repo event types are never written
    PASS  all 10 agent-teams/* types are omitted from the session log
  2/4 harness-recognized types are still written
    PASS  known first-party type is written
    PASS  unknown custom type is omitted too
  3/4 session write failures are contained
    PASS  append failure does not escape appendTeamEvent
  4/4 captain session resolution
    PASS  offline captain falls back to the caller session
    PASS  live captain session wins over the fallback
  all checks passed  (exit 0)

Refs #8