fix(sleep): don't show 'awaiting confirmation' for a persisted alarm

[dannymcc]

Problem

On the Sleep tab, the caption under Set band alarm read "Alarm sent, waiting for the strap to confirm." on a fresh open, even when the user never tapped the button this session.

Root cause

The caption fell through to the pending/awaiting text whenever a persisted alarmEpoch existed. That epoch is restored from SharedPreferences on launch (an alarm set in a previous session), but the strap-confirmation state machine (AlarmConfirmation) is session-scoped and records no SET on a cold open. So the fallthrough fired the "awaiting confirmation" caption with no user action.

Fix

Route the caption purely through the session-scoped confirmation flags (alarmConfirmed / alarmPending / alarmUnconfirmed) rather than the persisted epoch. On a fresh launch all three are false, so the caption is idle (nothing shown). The persisted epoch is deliberately no longer an input.

• Extracts a pure, public alarmStatusCaption({confirmed, pending, unconfirmed}) so the "only speak after an in-session SET" rule is unit-testable.
• Narrows the context.select tuple to (alarmConfirmed, alarmPending, alarmUnconfirmed) — exactly the fields the caption reads. The grace timer's notifyListeners() flips alarmPending true→false, changing the tuple, so the pending→unconfirmed transition still triggers a rebuild.
• Adds test/sleep_alarm_caption_test.dart covering the mapping and driving the real AlarmConfirmation transitions (fresh session → no caption; SET → pending → unconfirmed; event 56 → confirmed; disable → idle).

Scope

UI caption only. Does not touch the BLE alarm delivery path (tracked separately as #119).

Closes #118

Summary by CodeRabbit

• Bug Fixes

  • Improved Sleep Coach alarm status messaging to reflect the current session state.
  • Prevented alarm captions from appearing when no in-session alarm confirmation exists, even if an older alarm record is present.
  • Ensured captions update correctly for pending, confirmed, unconfirmed, and disabled alarm states.

• Tests

  • Added regression coverage for alarm caption timing, precedence, and clearing behavior.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 2ef0cb79-7ddb-4907-b405-0b6fa5a342ac

📥 Commits

Reviewing files that changed from the base of the PR and between e90a4a3 and dc46697.

📒 Files selected for processing (2)

• lib/ui/insights/coach_cards.dart
• test/sleep_alarm_caption_test.dart

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📝 Walkthrough

Walkthrough

The Sleep Coach alarm caption now uses session-scoped alarm flags rather than a persisted alarm epoch. Tests cover idle, pending, unconfirmed, confirmed, disabled, and precedence states.

Changes

Alarm caption flow

Layer / File(s)	Summary
Session alarm caption state and UI wiring lib/ui/insights/coach_cards.dart	Adds alarmStatusCaption and updates the Sleep Coach card to derive captions and rebuild from the three session alarm flags.
Caption mapping regression coverage test/sleep_alarm_caption_test.dart	Tests caption behavior for each alarm state and verifies precedence across overlapping flags.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title is specific and matches the main fix: suppressing the alarm confirmation caption for persisted alarms.
Linked Issues check	✅ Passed	The caption now depends on session-scoped alarm flags, so a persisted alarm no longer shows the waiting message on fresh open.
Out of Scope Changes check	✅ Passed	The changes stay focused on Sleep caption logic and tests, with no unrelated feature work evident.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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