fix: restore session cancellation and heart-rate recovery

[ridecontrol]

Changes

• Restore the prior ride state when the end-session dialog is canceled with Escape, close, or backdrop; exclude prompt time and defer resistance settlement until confirmation.
• Reset ordinary new sessions without retaining prior ride metrics, saved identity, journey linkage, or course position; preserve explicit history continuation.
• Require valid heart-rate data before readiness, recover silent streams, and prevent stale setup, GATT completions, and retry timers from interfering with newer connections.
• Document the corrected lifecycle behavior.

Verification

• Local bun run ci passed on a811033: 400 tests, Biome, Tailwind diagnostics, TypeScript, and production build.
• Browser checks covered cancellation, preserved manual pause, fresh-session reset, and explicit history linkage.
• Chromium fake-device smoke verified heart-rate silence recovery using the same remembered device without re-pairing.
• Physical heart-rate monitor and OS reconnect timing remain hardware-dependent and were not verified.
• Local CI is the merge gate while GitHub Actions is unavailable.