[codex] v3.30 reduce audio overload in hallway alerts

[Anthonyiswhy]

Summary

This PR changes the hallway alert policy to reduce audio overload while keeping urgent/warning safety alerts available.

What changed

• Suppress spoken alerts for tracks beyond 3.2m using a beyond_voice_distance policy reason.
• Let close side-person alerts within 1.5m route even when the IMU says the user is still.
• Drop awareness and clear/path-clear messages when audio is already busy by default.
• Add global cooldowns for noncritical speech:
  • awareness: 10s
  • clear/path-clear: 12s
• Shorten awareness wording so it uses existing clip-style phrases, for example person on your left, 1.4 meters.
• Add regression tests for far-person suppression, side-pass alerting independent of IMU moving state, and noncritical audio dropping.

Why

The latest hallway run showed two related problems:

• Far 5-7m person tracks with noisy TTC were being spoken as if actionable.
• People passing nearby on the side were often detected but suppressed because IMU state said user=still.

The audio overload research also points toward keeping speech sparse because blind users rely on environmental sounds for orientation and hazard awareness.

Validation

• python3 -m pytest tests/test_blindnav.py tests/test_blindnav_v326.py -q
• Result: 206 passed in 12.64s

Field test needed before merge

Run hallway clip mode again and confirm:

• no more 5-7m person callouts
• nearby side-pass people are spoken more consistently
• audio feels less backed up / less chatty
• urgent obstacle warnings still come through

[Anthonyiswhy]

Field-log follow-up: the 2026-05-20 hallway run showed left-side people were detected, but two alerts likely felt missed because normal warning/awareness audio was already occupying the queue. Updated this PR in f592fc4 so busy-area speech is off by default and side-pass warnings route through urgent queue priority while keeping their policy tier as warning. Tests: python3 -m pytest tests/test_blindnav.py tests/test_blindnav_v326.py -q (208 passed).