feat: combine translation and reversible dictation workflows

[adamholter]

Purpose

This draft is the requested integrated comparison branch. The independently reviewable slices are:

• feat: make recording cancel shortcut configurable #1140 configurable recording cancel shortcut
• feat: add cleanup strength levels #1141 cleanup strength levels and history provenance
• feat: make saved AI transcript edits reversible #1142 reversible saved AI edits and streaming raw-text preservation
• feat: reprocess saved transcripts with AI cleanup #1143 reprocess a saved transcript with current AI cleanup
• feat: add dedicated translation dictation mode #1144 dedicated translation dictation mode

Maintainers can review and merge the narrow PRs independently; this branch proves the features coexist and provides one place to evaluate the complete workflow.

Integrated behavior

• configurable recording-scoped cancellation with safe fallback
• None/Light/Medium/High cleanup contracts
• raw/processed transcript version preservation, undo, redo, comparison, and reprocessing
• cleanup-level and translation-target provenance in History
• dedicated multi-target translation with fail-closed provider behavior
• conflict-aware settings, hotkeys, database migrations, IPC, and all current locales

Validation

• 296 passing tests, 0 failures, 5 macOS-expected Linux skips
• formatting, TypeScript, i18n, and renderer build pass
• all GitHub checks pass: tests, lockfile lint, CodeQL/static analysis, Linux, Windows, macOS x64, and macOS arm64
• live cleanup-level semantic fixture preserved every required fact and made High the most concise output
• six combined headless UI flows pass under independent process-tree watchdogs with zero console errors: cancel, cleanup settings, reversible edits, reprocessing, cleanup provenance, and translation
• hidden physical macOS cancel integration passes: registration succeeds, the callback fires exactly once, the accelerator releases, Dock remains hidden, and zero BrowserWindows are created
• every harness uses bounded launch/assertion timeouts and leaves no browser, Electron, Vite, listener, or temporary profile behind