feat: add optional live Codex memory panel

[Ray-7456]

What

Adds an optional local MCP App under plugins/codex-memory-panel so Codex desktop users can inspect Mnemon memories beside chat and see later writes without reloading. Project-directory associations select project stores; transferable global experience stays in a separate store. Aggregate browsing is read-only. Explicit write tools and a bundled skill support recall before development and saving verified lessons afterward.

Reads use a normalized CLI adapter. For Mnemon 0.2.10, SQLite online backup precedes immutable readonly CLI commands to include committed WAL data. File-change detection and MCP long polling drive updates. Resources are preloaded and previous runtime files are retained during local upgrades. Existing lifecycle hooks and the Go product core are unchanged.

Why

Related to #155. This draft is for discussing whether this optional package belongs in the main repository or a separate integration repository; it does not close the discussion issue. Native right-panel rendering has been verified in Codex desktop.

Validation

• npm ci --ignore-scripts --no-audit --no-fund succeeded from the standard npm registry.
• npm test passed all 3 portable regressions: optional engine fields, rejection of missing required fields, and MCP resource availability after its UI directory is replaced.
• Earlier local checks covered committed WAL snapshots, store isolation, duplicate writes, cross-process associations, UTF-8 request bodies, SDK roundtrips and live preview updates.
• Reviewed all 24 changed files and the published commit history for private content. Local configuration, project names, memory records/databases, logs, screenshots and internal planning documents are excluded. The single public commit uses GitHub's noreply author address.
• make test was not run: this Windows environment has neither Go nor make, and the attempted official portable Go download was interrupted. The required upstream Go checks remain outstanding; this PR stays draft.

Limits and release-note impact

Codex controls navigation: the global rail entry opens fullscreen, while the thread entry remains under More tools. This package cannot promote the launcher or redirect the rail click into the current chat's right panel. Live updates were checked in the equivalent local preview; native rendering alone does not establish live updates in every host session. Project discovery has a manual fallback. Future breaking engine changes may require an adapter update.

Release-note impact: optional Codex desktop integration; existing memory commands, Go core and lifecycle-hook integrations retain their behavior.

Checklist

• Deterministic tests pass (make test) — outstanding; local toolchain unavailable
• Relevant E2E/process/Docker boundaries pass (make test-integration, when affected) — no Go/Agency boundary changes
• New/changed behavior has portable regression coverage
• Documentation updated
• User-facing release-note impact described

[Ray-7456]

The CI run currently reports action_required (run 37955199546), so the required upstream checks have not passed yet. The portable plugin regressions pass locally. This PR remains draft pending CI and the integration discussion in #155.