feat: connect managed MCP clients through independent Nova.app

[bigduu]

Summary

The Nova plugin previously ran desktop APIs directly in Bamboo/Bodhi's process chain on macOS. It now runs nova mcp: macOS connects to the independently installed Nova.app before any desktop initialization or permission request; Windows and Linux retain the existing stdio server.

An unavailable app fails with installation and Nova-only reconnection guidance instead of falling back to host-owned desktop APIs. Existing direct CLI, --connect, HTTP, and the optional Chrome DevTools launcher remain compatible. Documentation explains independent app installation, keeping Bodhi open during reconnection, and the remaining signed-release/TCC upgrade acceptance gates. The published v0.2.1 release is unchanged and predates this entrypoint.

Closes #33. Part of bigduu/Zenith#185.

Test Plan

• Real connector processes complete initialize/tools-list/ping while stdin remains open; two different plugin connector PIDs reuse one test-owned service.
• Missing-service tests fail closed without launching installed apps, touching desktop APIs, or corrupting MCP stdout. CLI tests reject conflicting modes; Linux CI now executes the managed stdio path.
• Local: library 106, CLI 3, managed transport 3, DevTools launcher 2, extension 122, and native-host 30 tests passed.
• Formatting, diff checks, strict macOS and Windows ARM64 all-target Clippy, and release/static/mock packaging checks passed.
• Full existing macOS app/stdio suites and Linux execution are covered by CI. Windows validation here is cross-compilation, not Windows GUI execution.
• Real signed installation, permission grants, and Bodhi/Nova upgrade acceptance are tracked separately in [nova] feat: verify signed app distribution and host upgrade permissions #36; they are not claimed by the hermetic transport tests.

Screenshots

Not applicable: this slice changes CLI/plugin routing and documentation; no graphical UI is changed.

[bigduu]

Independent agent review completed for exact head 7f18e07a01cbed78b32b4f0c008c53bb49eb1557 against 67831322dbed19de754f31768c3231ee582c1aa8.

No blocking finding introduced by the diff or required for #33's acceptance slice. The reviewer traced macOS's early pure-connector return, non-macOS stdio, manifest compatibility, ongoing streaming, independent service lifetime and the explicit source/release/TCC limits in documentation.

Independent local verification: 3 CLI tests and 3 managed transport tests passed. Additional real-process fixture probes passed for simultaneous connectors, keeping the second usable after the first exits, and insecure-runtime-directory rejection with clean MCP stdout.

Current exact-head CI: all six jobs passed in https://github.com/bigduu/Nova/actions/runs/33946225704, including the existing macOS app-service/stdio suite and the new native Linux managed-stdio test.

The pre-existing connector EOF / blocking stdin lifetime issue was reproduced through both the new entrypoint and unchanged --connect; it is recorded separately in #40. It does not change this PR's explicit manual-reconnection contract. Signed installation and real TCC upgrade verification remain in #36.