Slack huddles in Arc browser never auto-detected as meetings

Bug Description

Slack huddles running in the Arc browser are never auto-detected as meetings. Manual meeting start works, but automatic detection never fires.

Root Cause (from source)

The Slack detection profile in apps/../crates/screenpipe-engine/src/meeting_watcher/shared/profiles.rs (~line 253) defines:

// Slack Huddle (browser + desktop)
MeetingDetectionProfile {
    app_identifiers: AppIdentifiers {
        macos_app_names: &["slack"],
        windows_process_names: &["slack.exe"],
        browser_url_patterns: &["app.slack.com/huddle"],
        browser_title_patterns: &[],   // <-- empty
    },
    ...
}

Three compounding gaps for Arc users:

1. URL never matches. In a browser, Slack huddles run inside the same workspace tab — the URL stays https://app.slack.com/client/T.../C... and never becomes app.slack.com/huddle/.... The /huddle URL only appears when opening a huddle link directly. /client/ URLs are deliberately rejected as attribution evidence (arc_slack_client_url_does_not_auto_start_when_unattributed test).

2. No title fallback. The scanner (ui_scan/pipeline.rs: db_find_browser_meetings) falls back to window-title matching for browsers like Arc that don't expose URLs via AX — but Slack's browser_title_patterns is empty. Google Meet has browser_title_patterns: &["Meet"]; Slack has nothing.

3. AX scan can't help. Arc doesn't expose page URLs via AXDocument, and the huddle's "Leave huddle" AXButton lives in a popover the scan never reaches without a DB hint pointing it at the right window.

Evidence from a live install

• 2,576 of 2,642 Arc frames in the last 24h have browser_url populated — URL capture works fine
• All Slack URLs captured are app.slack.com/client/... — zero /huddle/ URLs ever
• The huddle window title IS captured in frames: "Huddles - leadgen - Slack" — the signal exists, it's just never consulted

Expected Behavior

An Arc huddle window with title like "Huddles - <workspace> - Slack" should trigger the Slack profile the same way Meet's "Meet" title pattern does.

Proposed Fix

Add a title pattern to the Slack profile:

browser_title_patterns: &["huddle"],  // or "Huddles"

...plus a unit test mirroring the existing arc_slack_client_url_does_not_auto_start_when_unattributed test but with title: "Huddles - workspace - Slack".

Note on false positives: a window titled "Huddles" without an active huddle is rare (it's the huddle list view), and the state machine still requires call-control signals or audio activity to confirm — so a bare title match alone shouldn't phantom-fire. Matching case-insensitively on "huddle" would also cover 1:1 huddle titles ("Alex N (DM) ... huddle").

Environment

• macOS (Apple Silicon)
• Arc browser (Chromium)
• screenpipe app v2.7.x (latest)
• Slack huddles run in Arc tabs, not the Slack desktop app