Fix Now Bar Live Update tap routing to Pixel Ambient Music - #3

Reproduced navigation defect

The Now Bar Live Update contentIntent currently launches Ambient Music Mod's MainActivity, which sends the user to the Mod configuration rather than the Pixel Ambient Music app.

Fix

• Route the notification PendingIntent to com.google.intelligence.sense.NOW_PLAYING_HISTORY, explicitly scoped to the paired com.kieronquinn.app.pixelambientmusic package.
• Reuse the exact exported HistoryActivity action already used by AMM's own "History" button.
• Keep Android Live Update / promoted ongoing shape, channel, timeout and current title/artist unchanged.
• Add an instrumentation assertion for action, package and activity intent flags.

Important limitation

Pixel Ambient Music 1.3.5 has a verified exported history destination but no verified public per-track details intent. This fixes opening the wrong app but does not claim automatically selecting the exact recognised song; no speculative extras or undocumented URI query parameters were added. The latest recognised song should be in history after successful write; verify on hardware. A true direct-to-song route requires separate validation against the paired PAM build.

Verification pending

• Compile and instrumentation test build in CI.
• Hardware on Galaxy S25 / Android 17 / One UI 9 using both paired, same-signer APKs.
• Tap notification and Now Bar, verify same destination.
• Observe missing PAM case and possible unexpected ActivityNotFoundException.
• Verify recognition, crash traces, and promoted eligibility separately (outside this navigation PR).

Do not merge until actual device testing passes.