[enaboapps]

When native text reading works but fallback input tracking is unavailable, prediction polling repeatedly reset the cached batch. The scanning keyboard then treated unchanged suggestions as replacements and cleared them while their row was active.

Preserve native context caching independently of fallback tracking. Keep genuine edits, focus/caret/selection changes, explicit resets and stale acceptance invalidating old choices. Input-observer failure still disables tracked-text fallback.

Validation:

• Required frontend lint, 158 frontend tests, 5 script tests and build pass locally.
• Rust format, Clippy and full tests pass: 477 unit tests and 7 configuration tests; one existing ignored benchmark.
• Added worker/service regressions for unavailable tracking with native reads, genuine changes yielding identical words, editing/casing/selection, and pending resets.
• Added grouped/linear, forward/reverse, manual/automatic scanning regressions for unchanged replies, timing, pass limits and exactly-once selection.
• Independent latest-head review is clean on 7928e603857adc0139816df9358d1eddfa08c158.
• Mac VM: development-signed build launched; J/K/L navigated the action menu and keyboard, and selected Space and W each typed once in disposable TextEdit content with focus preserved. Predictions remained empty, so suggestion stability could not be qualified natively. Supplied the debug build's database at its compile-time resource path for the test; removed that temporary resource afterward.
• Windows ARM VM: native build succeeded. Parallels virtual Insert/F1 switches navigated the menu to Type here; the keyboard did not become visible and later switch presses produced no observable scan movement. This matches the previously documented VM qualification limitation; no root cause or product regression is asserted.
• VM settings restored byte-for-byte, test app/editor stopped, previous Windows build restarted, and Mac returned to suspended. The signed host Mac app (PID 55560) remained untouched.
• All required CI checks pass on 7928e60, including native Mac and Windows packaging, dependency audit and CodeQL. The unchanged frontend setup-dialog test timed out on the initial run; the failed-job rerun passed (run 35518638988, attempt 2).

Keep draft: native suggestion stability still requires qualification on both VMs.

No settings or BLE changes. No merge or release requested.

Closes #805.