ci: add trusted Gradle cache policy

[MohamadJaara]

Goal

Reduce CI cache restore time and prevent untrusted or release workflows from reading or writing shared Gradle state.

What changed

• Replaced the monolithic Warp Gradle cache with gradle/actions/setup-gradle.
• Added one reusable Java and Gradle setup action for cache policy, wrapper validation, and optional KVM setup.
• Enabled Gradle task-output caching only for the trusted develop lifecycle.
• Isolated Gradle homes on long-lived self-hosted release-generation and QA runners.
• Kept the Android UI-test AVD cache separate.

Cache trust model

Context	Restore	Write
Push to develop	Yes	Yes
Same-repository PR targeting develop	Yes	PR scope only
Merge queue targeting develop	Yes	No
Fork PR	No	No
Main/release push or release publication	No	No
Manual or scheduled generation	No	No

Impact

Develop and trusted PR builds can reuse smaller, Gradle-aware cache segments without repeatedly restoring the previous 8+ GB archive. Release, generation, fork, and unrelated branch workflows do not consume shared Gradle cache state.

Validation

• All changed workflow and action YAML parses successfully.
• The new composite action passes the repository's pedantic Zizmor policy.
• Remaining cache references were audited; only the intentional AVD cache remains on Warp caching.

[github-actions]

Test Results

2 225 tests  ±0   2 225 ✅ ±0   2m 11s ⏱️ +24s
  241 suites ±0       0 💤 ±0 
  241 files   ±0       0 ❌ ±0 

Results for commit de8e616. ± Comparison against base commit 4227a16.

♻️ This comment has been updated with latest results.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.52%. Comparing base (4227a16) to head (de8e616).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #5137   +/-   ##
========================================
  Coverage    50.52%   50.52%           
========================================
  Files          671      671           
  Lines        24604    24604           
  Branches      3832     3832           
========================================
  Hits         12430    12430           
  Misses       11029    11029           
  Partials      1145     1145           

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