fix: keep native helper bundle generated-only

[daniele21]

Outcome

Restore exact-source build cleanliness for LOCAL REAL_ENVIRONMENT and production packaging by treating the native capture helper .app as generated output rather than tracked source.

Root cause

build.sh already deletes and regenerates build_assets/ClosedRoomNativeCapture.app, including a versioned Info.plist. The tracked plist still contained an older product version, so an exact build rewrote tracked source. run_local_real_environment_suite.py correctly failed closed when it detected that dirty checkout; the same mutation could also violate production-build cleanliness.

Change

• ignore the complete generated build_assets/ClosedRoomNativeCapture.app/ bundle;
• remove the obsolete tracked generated Info.plist;
• add a regression contract proving the plist is untracked/ignored and that build.sh still regenerates and embeds the helper app.

No runtime, capture, UX, privacy, or cloud behavior changes.

Axes

• PRODUCT: PRODUCT_NONE
• DELIVERY: INTEGRATION
• VALIDATION: selector-owned; packaging/release identity should fail safe to FULL
• EXECUTION: REMOTE_AUTOMATED for deterministic gates; REAL_ENVIRONMENT remains required afterward on the new exact dev candidate.

Evidence

The failed physical run on dev@a47b4200… built a successful clean-manifest ad-hoc artifact but stopped before child physical checks because the build rewrote the tracked helper Info.plist. This PR removes that source mutation rather than weakening the clean-checkout gate.