fix: manage derived state across lifecycle - #642

Summary

• make uninstall --plan and confirmed --purge-data resolve the installed copy’s runtime state root, including host-declared AGENT_BUNDLE_STATE_ROOT, and preserve it under --keep-data
• report effective and legacy state roots from doctor, including existence, writability, and AB7332 for retained pre-feat(runtime): separate the framework state root from the plugin code root #640 state
• cover generated installer and packed state-writing lifecycle behavior; update English/Chinese docs and diagnostics

Validation

• pnpm build
• pnpm typecheck
• pnpm lint
• pnpm test:unit
• pnpm test:projection
• pnpm docs:site:build
• pnpm exec rstest --config rstest.config.ts packages/agent-bundle/tests/packed-readonly-state-root.test.ts
• targeted host-install, packed CLI, and installer-entry suites

Deslop

• GPT-5.6 Sol, 1 edit: removed the superseded retainedPluginData field and reused the external-state path decision for remnant receipts.

Self-review

• Reviewer: Claude Fable 5.1 Thinking High
• Initial findings: manifest-declared state roots were not retained through a Cursor keep→purge cycle; web-data derivation diverged under symlinked roots; Codex keep-data reporting included in-tree state removed by the host; AB7316/Codex docs were stale.
• Disposition: fixed all findings with remnant receipt state-root metadata, a shared web-data-root helper plus symlink regression, corrected Codex path/outcome logic, and docs/capability/changeset updates. CI then exposed an eager optional-runtime import; the final implementation keeps lifecycle code runtime-free while runtime-backed tests pin identical root derivation.
• Final re-review at 55d19903d: no concrete merge risks remain.

Closes #641