Handle spacing and capitals for scanned punctuation

[enaboapps]

Closes #872.

Change

• The scanned keyboard treats . , ! ? : ; as prose punctuation. It removes a preceding space only when the keyboard's own insertion is still verified, then inserts one space after the mark. The Numbers-page period remains literal for decimals.
• A sentence-ending mark activates the keyboard’s visible one-use Shift state for the next letter without changing manual Caps lock. Tapping that automatic Shift turns it off. Sentence-start predictions retain title case, and accepted suggestions satisfy pending capitalization; their trailing spaces can be removed before punctuation.
• A content-free input activity epoch and foreground identity invalidate ownership on external input. Switch assignment changes update the ignored-key set. Editing and navigation clear pending capitalization; shortcut output remains unchanged. Native observation retries after hook failure, and a disabled macOS tap stops before replacement. Persisted schemas are unchanged.

Validation

• npm run lint — pass
• npm test — pass (223 UI tests, 5 update-feed tests)
• npm run build — pass
• cargo fmt --manifest-path src-tauri/Cargo.toml --check — pass
• cargo clippy --manifest-path src-tauri/Cargo.toml --all-targets -- -D warnings — pass
• cargo test --manifest-path src-tauri/Cargo.toml — pass (538 Rust unit tests, 7 integration tests; 1 ignored)
• Windows 11 Parallels VM: built head ce32bdf with Node 24.19.0 and the ARM64 Windows Tauri debug target. With Notepad foreground, assigned switch-key events sent through Windows SendKeys opened the scanned keyboard and selected Space, period, a, comma, Space, b, the Numbers page, 1, decimal point, and 6. The resulting text matched . A, b1.6: the owned space was removed before the period, one was inserted after punctuation, the next letter was capitalized, the extra Space was suppressed, and the Numbers-page period stayed literal. The keyboard overlay remained visible without taking focus. Original VM switch and scanning settings were restored after the test.
• Follow-up Windows 11 VM run: built head a3aefcd and used assigned switch-key events in Notepad to enter a space, period, and letter. The overlay showed active “Shift / Next key” with uppercase letters after the period, then Shift inactive after the letter; resulting text matched . A. Both VM settings files were restored byte for byte after testing, and Switchify was restarted with those originals.
• Windows scope: this was an ARM64 native debug build in the Windows 11 VM using scripted switch-key events; it was not a physical switch device or installer validation. macOS event-tap recovery is covered by the Rust lifecycle test, not a live macOS permission-toggle test.
• Independent review of latest head a3aefcd: no remaining actionable findings.