fix: integrate video queue, capture health and permission probes

[swellweb]

Scope

Focused maintenance integration of #194, #195 and #177, preserving the original commits and contributor attribution. Thank you @Betafer for these focused fixes and tests.

• fix(sender): preserve encoded frame references under backpressure #194: reserve queue capacity before encoding so HEVC/H.264 reference frames are not discarded afterwards.
• fix(sender): distinguish idle capture from a stalled pipeline #195: distinguish event-driven idle capture from genuine stalls and guard delayed recovery against replacement sessions.
• feat: expose non-interactive permission status #177: expose read-only permission status from both application binaries without starting the normal session.
• Follow-up input fix: explicitly attach the relayed modifier flags to mouse button, drag, move (including edge), and scroll events on the Sender. Six CGEvent construction tests cover Shift/Command selection and release, all drag/button types, click state and scrolling. No input protocol or Receiver changes.
• Resolve the shared capture-entry conflict by keeping BOTH the usable-frame guard and pre-encode queue budget.
• Add a source integration guard, bounded permission-probe smoke tests for both binaries, CI coverage for both architectures, and documentation in docs/Automation.md.

Local validation (Apple Silicon)

• Full Sender build passed.
• Full Sender XCTest suite: 134 tests passed, zero failures.
• Standalone production capture-health suite: 17 tests passed (also included in the 134 above).
• Production video queue budget and both capture-path source guards passed.
• Receiver: 654 checks passed (67 parser, 562 input queue, 12 watchdog, 13 display profile).
• Receiver application build and dependency bundling passed.
• Two consecutive permission probes per built application passed with valid output and bounded process exit.
• All five shared localizations passed validation.
• git diff --check passed.

Before merge / release

• Re-run combined CI on Intel and Apple Silicon for the pointer-modifier follow-up. All four jobs passed on the earlier integration commit 126141a.
• Live Sender/Receiver regression run: audio, 5K/HiDPI, colors, cursor, keyboard/shortcuts, reconnect, static desktop and resume.
• Check supported older macOS packaging separately; local Homebrew builds are not proof of backward compatibility.

This is a test candidate, not a release. main, installed applications, permission settings and version numbers are unchanged. No signing-policy changes from #196 or other feature PRs are included. Keep the source PRs open until this integration has passed validation.