fix(chat): correct push notification click-through URL

[penso]

Summary

• Push notification "View" CTA was navigating to /chat/session:42 which doesn't match any SPA route, causing a 404
• Fixed URL construction to produce /chats/session/42, matching the frontend sessionPath() in router.ts
• Extracted push_notification_url() helper with unit tests

Closes #773

Validation

Completed

• cargo +nightly-2025-11-30 fmt --all -- --check passes
• cargo test -p moltis-chat push_notification_url — 3 tests pass
• No other callers construct push URLs with the old /chat/ prefix

Remaining

• just lint
• just test
• Manual QA: enable push notifications, trigger a heartbeat, tap the notification CTA

Manual QA

1. Enable push notifications in Settings > Notifications
2. Add a heartbeat cron job
3. Wait for the heartbeat to fire
4. Tap "View" on the push notification
5. Verify it navigates to the correct chat session (no 404)

[greptile-apps]

Greptile Summary

This PR fixes a broken push notification click-through URL by replacing the old /chat/session:42 construction with a new push_notification_url() helper that produces /chats/session/42, correctly matching the frontend sessionPath() in router.ts. The change is small and well-tested with three unit tests covering the common case, nested keys, and keys without colons.

Confidence Score: 5/5

Safe to merge — the fix is correct, well-tested, and the only remaining note is a minor feature-gate alignment.

All findings are P2 (style/cleanup); the logic fix itself is correct and unit-tested. No data integrity or runtime issues found.

No files require special attention.

Important Files Changed

Filename	Overview
crates/chat/src/channels.rs	Introduces push_notification_url() helper fixing the URL from /chat/session:42 → /chats/session/42; adds three unit tests. Minor: function lacks the same #[cfg(feature = "push-notifications")] guard as its only caller.

Sequence Diagram

sequenceDiagram
    participant Runtime as ChatRuntime
    participant Channels as channels.rs
    participant PushSvc as PushNotificationService
    participant Client as Mobile Client

    Runtime->>Channels: send_chat_push_notification(session_key, text)
    Channels->>Channels: push_notification_url(session_key)
    Note over Channels: "session:42" → "/chats/session/42"
    Channels->>PushSvc: send_push_notification(title, summary, url, session_key)
    PushSvc-->>Client: Push notification with url="/chats/session/42"
    Client->>Client: Tap "View" CTA
    Client->>Client: Navigate to /chats/session/42 ✅
    Note over Client: was /chat/session:42 → 404 ❌

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_{Reviews (1): Last reviewed commit: "fix(chat): correct push notification cli..." | Re-trigger Greptile}

[codspeed-hq]

Merging this PR will not alter performance

✅ 39 untouched benchmarks
⏩ 5 skipped benchmarks¹

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_{Comparing precious-sunflower (e9fcfaf) with main (e11d2ba)}

Footnotes

1. 5 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[codecov]

Codecov Report

❌ Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
crates/chat/src/channels.rs	92.85%	1 Missing ⚠️

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