feat: insert raw transcripts into the original application

[douglasjarquin]

Closes #6

Summary

• Captures the original frontmost PID, bundle identifier, focused Accessibility element identity, role, and secure-field state at dictation start.
• Keeps Oigo accessory/menu/HUD surfaces nonactivating.
• Persists raw.txt before replacing the general pasteboard, then revalidates the target and sends one PID-bound Command-V only when safe.
• Falls back to copy-only for changed applications or focus, missing Accessibility permission, unavailable focus, noneditable roles, and secure fields.
• Persists insertion claims and outcomes, retains the final raw transcript on the clipboard, and dismisses terminal status HUD messages briefly without blocking.
• Adds deterministic target-validation, secure-refusal, copy-fallback, event-boundary, and restart-safe one-shot coverage.

Validation

• SwiftPM build and spike, issue [02/13 · MVP] Build the native menu-bar shell and dictation state machine #3, issue [03/13 · MVP] Add durable microphone capture and crash-recoverable sessions #4, issue [04/13 · MVP] Add on-device transcription and saved-audio retry #5, and issue [05/13 · MVP] Insert the raw transcript into the original application #6 contract harnesses pass.
• Xcode native build passes with DEVELOPER_DIR=/Applications/Xcode.app/Contents/Developer.
• Native TextEdit probe pasted the exact transcript once and read it back from the document with the transcript retained on the clipboard.
• Native Xcode probe identified AXOutline as noneditable, returned copy-only, and retained the raw transcript on the clipboard.
• Native app launch kept the existing frontmost application active.

Host limitations

• Full live dictation completion could not be exercised because Apple-managed speech assets are unavailable on this host.
• Safari, Visual Studio Code, and Slack are not installed on this host; their limitation is documented rather than covered by an adapter.