merge: stack LeanBitLab v4.0.2

[AsafMah]

Summary

Stack the pinned LeanBitLab/LeanType v4.0.2 release (0477ef83) above the v3.9.9 integration in #122. This PR intentionally targets merge/upstream-v3.9.9, so reviewers see only the v3.9.9 → v4.0.2 delta; after #122 merges, retarget this PR to dev. upstream/main was not merged because it is already one badge-only commit past v4.0.2.

The update brings v4 JNI/lifecycle hardening, pointer and InputConnection stability fixes, first/next-word controls, background-service controls, immediate autospace, translation-history improvements, and restored dictionary/input reliability.

Fixes #123.

Fork decision: retain Java fallback gesture typing

Upstream v4.0.2 removes the Java gesture engine and requires a compatible native gesture library. LeanTypeDual deliberately retains both methods:

• Fallback remains the default and works with the built-in dictionary JNI library.
• Native remains selectable when a compatible external/system gesture library is available.
• Restored lifecycle ownership covers startup initialization, dictionary/keyboard-triggered asynchronous index builds, accepted-word learning, and cancellation on IME destruction.
• Ported upstream's pre-removal hardening: shared keyboard executor, atomic build suppression, bounded per-letter indexes, OOM protection, cancellation, and serialized learning-data writes.
• Preserved the fork's script-aware key maps and canonical lowercase fallback candidates.
• Added an end-to-end regression that runs Suggest.getSuggestedWordsForBatchInput with native unavailable, waits for asynchronous index construction, and returns hello.

Merge decisions

• Preserve com.asafmah.leantypedual, version 3.10.0 / code 4000, privacy flavors, two-thumb features, README, badges, and Fastlane metadata.
• Combine v4 immediate autospace with the fork's combining-mode trailing-space precedence; both behaviors have focused tests.
• Keep Blocklist and new Background Services navigation routes.
• Move generic gesture autospace controls to Gesture Typing while hiding them when manual two-thumb spacing makes them no-ops.
• Restore fallback/native selection in Gesture Typing and the Welcome Wizard; show native library download only for the native method.
• Preserve merge: sync LeanBitLab v3.9.9 #122's snapshot-consistent multilingual suggestion workers and independent JNI weight arrays while accepting v4's 500 ms bounded wait and next-word controls.
• Remove two catalog rows confirmed HTTP 404; all remaining 268 dictionary URLs returned HTTP 200, including 17 successful timeout retries.

Verification

• All four gates pass: compileOfflineRunTestsKotlin, compileOfflineliteRunTestsKotlin, compileStandardRunTestsKotlin, and compileStandardfullRunTestsKotlin.
• Final full Offline debug suite: 309 tests, 10 failed, 1 skipped. No new failing names versus merge: sync LeanBitLab v3.9.9 #122 (294 tests, 11 failed, 1 skipped); upstream fixes remove the previous autocorrect-revert failure and the stale catalog failure is removed.
• Final Offline runTests suite: 309 tests, 4 failed, 1 skipped, exactly the same four environment-dependent parser failures as merge: sync LeanBitLab v3.9.9 #122 (294 tests, 4 failed, 1 skipped).
• Focused Java fallback ownership, fallback casing, async dictionary, AppUpgrade, SettingsContainer, Thai immediate-expansion, and immediate/combining autospace tests pass.
• Merged manifests retain LeanTypeDual package IDs/version, exactly one Startup provider, largeHeap/predictive-back flags, and INTERNET only in Standard/Standard Full.
• High-effort independent review found no blocker; remaining caveat is an on-device fallback lifecycle smoke before release tagging.

Release sequencing

1. Review and merge merge: sync LeanBitLab v3.9.9 #122 into dev.
2. Retarget this PR from merge/upstream-v3.9.9 to dev; verify the diff remains only v4.0.2.
3. Merge this PR.
4. Reconcile draft release PR Release LeanTypeDual 3.11.0 #120 with updated dev, rerun capitalization/signing/device checks, then make 3.11.0 release-ready.

Do not merge #120 before both upstream layers are settled.