Spoken symbols, model loading state, and UX fixes

[andyhtran]

Summary

• Spoken symbols expansion: add slash/pipe symbols, a supported-symbols list popover in settings, and a SpokenSymbolsCatalog that generates the list from live rules
• Per-edge word boundaries: replacement processor now anchors \b independently on each edge of find, so c++ anchors left-only and space-padded rules anchor their word side
• Model loading state machine: replace scattered isModelLoaded/isModelDownloading booleans with a ModelLoadState enum, generation-tagged preload tasks, and phased progress reporting (checking → downloading → preparing)
• Pulsing processing icon: replace static SF Symbols for transcription/edit-mode with animated pulsing bars (orange for transcription, purple for edit-mode), driven by a 10fps frame timer
• Fn key fixes: move stuck-state recovery before the re-entry guard so it actually fires; remove the hold-duration gate so press-and-hold-then-release toggles the same as a quick tap
• Recording flow: toast on too-short recordings (<1s), capture actual file size and "auto" language in failed recording metadata
• Paste reliability: remove the changeCount check in copyAndPaste that could silently skip the paste step
• Launch popover: gate on isMenuBarVisibilityHintAvailable before scheduling, so it never fires after the hint is exhausted

Test plan

• Verify pulsing bars appear during transcription and edit-mode, with distinct colors
• Verify model loading shows phased progress (checking/downloading/preparing) and recovers from failure
• Test spoken symbols: slash, pipe, back slash, hyphen all convert correctly
• Open the spoken symbols list popover from format settings and verify it shows all categories
• Verify Fn key tap and long-hold both toggle recording
• Confirm too-short recording (<1s) shows a toast instead of silently discarding
• Verify clipboard paste works reliably after transcription

🤖 Generated with Claude Code