Fix empty Teams meeting titles by waking Electron a11y tree

[execsumo]

Problem

Teams meeting titles were never captured, so transcripts fell back to the generic Meeting filename. The logged error was extractMeetingTitle: windows query failed … axErr=-25211 (kAXErrorAPIDisabled) at every meeting start.

Root cause

Teams is an Electron/Chromium app whose accessibility tree stays dormant until a client requests it. AX reads of its windows/titles/roster failed even though Heard itself is trusted (stable Developer ID signing + live AXIsProcessTrusted). The code only ever read the tree — it never sent the signal to build it.

Fix

• Set AXManualAccessibility=true on the Teams app element at detection (enableMeetingAppAccessibility) to wake the tree.
• The build is async and the join-time set can time out against a busy Teams, so the 15s roster poll re-nudges while the roster is empty and re-extracts the title until non-empty.
• The late-captured title is pushed into the live session via RecordingManager.updateTitle in onMeetingEnded (parallel to updateRosterNames), before the filename is built at write time. RecordingSession.title is now var.

Diagnostics (Developer Mode)

So the next real meeting validates the title fix and yields data to retune the never-verified roster parser:

• Meeting-start anchor + per-poll timeline lines.
• RosterReader.diagnosticTreeDump — bounded (depth ≤ 9, ≤ 500 nodes) outline of Teams' real AX tree, emitted up to 3×/meeting while the roster is empty. Unit-tested for structure, truncation, node budget, and depth.

Also

Fixes 4 main-actor concurrency warnings (future Swift 6 errors) in the screen-capture permission observer via MainActor.assumeIsolated.

Testing

swift build clean; swift run HeardTests → 185/185 pass (+4 new dump tests).

Title fix should resolve the filename issue immediately; roster reading is now unblocked but unverified pending a real-meeting tree dump.