Restore PR build cache parity

[AnthonyRonning]

Summary

• restore missing PR build caches for Tauri CLI, sccache, Gradle, Bun, Homebrew, and Xcode where they match the signed build workflows
• add a master-only iOS simulator ONNX cache warmer so new PR branches can restore the simulator ONNX cache from the default branch
• keep PR builds unsigned and without signing secrets

Why

PR iOS builds were paying a cold ONNX source build because the simulator ONNX cache is only created in pull_request scope. GitHub does not make a cache created for one PR branch generally available to future PR branches, so this would recur. The new warmer creates the same simulator cache key on master, where future PRs can restore it.

Validation

• workflow YAML parsed with Bun + yaml
• git diff --check
• checked workflow-only diff and checkout credential settings
• pre-commit hook: Prettier, frontend build, Bun tests

No package versions, dependencies, or lockfiles changed.

Summary by CodeRabbit

• Chores
  • Added sccache and expanded caching across Android and desktop (macOS/Linux) CI to speed Rust builds and report cache stats.
  • Added verification and pinned installs for build tooling and expanded caching of tool binaries to stabilize CI.
  • Added a warm iOS simulator ONNX Runtime cache job to reduce PR rebuilds.
  • Moved Xcode setup earlier and unified Homebrew cache keys to improve cache reuse in mobile workflows.
  • Updated Android/Gradle cache keys and made Tauri CLI installs version-gated in CI and release workflows.

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📝 Walkthrough

Walkthrough

This PR improves CI build performance by adding Bun/Gradle/Homebrew caches, installing and configuring sccache for Android/desktop builds, adding a warm iOS ONNX Runtime simulator cache job, and aligning mobile Homebrew cache keys.

Changes

Build Performance Optimization via Strategic CI Caching

Layer / File(s)	Summary
Android build acceleration: Bun and Rust caching .github/workflows/android-pr-build.yml	Adds Bun dependency caching and Gradle caches/wrapper caching; installs a pinned sccache release (with checksum), caches sccache and ~/.cargo/bin for a pinned Tauri CLI, and configures RUSTC_WRAPPER/SCCACHE_DIR/SCCACHE_CACHE_SIZE=2G in GITHUB_ENV.
Desktop macOS & Linux build acceleration: sccache .github/workflows/desktop-pr-build.yml, .github/workflows/desktop-build.yml	macOS: caches Homebrew artifacts, installs/links sccache via Homebrew, caches Mozilla sccache directory, and sets sccache env vars; Linux: downloads/verifies pinned sccache tarball, caches ~/.cache/sccache and ~/.cargo/bin, and prints sccache --show-stats after builds.
iOS ONNX Runtime simulator artifact caching & Homebrew key alignment .github/workflows/mobile-build.yml, .github/workflows/mobile-pr-build.yml	Repositions Setup Xcode earlier in iOS builds, adds warm-ios-pr-onnx-cache job to warm ONNX Runtime simulator artifacts (builds on cache miss and verifies the .xcframework), and switches mobile PR Homebrew cache keys from PR-scoped to shared keys.
Tauri CLI version-gated install .github/workflows/android-build.yml, .github/workflows/release.yml, .github/workflows/desktop-build.yml, .github/workflows/mobile-build.yml, .github/workflows/mobile-pr-build.yml, .github/workflows/android-pr-build.yml	Standardizes installing tauri-cli v2.9.2 by detecting cargo-tauri --version and only running cargo install tauri-cli --version ... --locked --force when the installed version differs; otherwise logs the required version is present.
Gradle cache key path updates .github/workflows/android-build.yml, .github/workflows/release.yml	Updates Gradle cache hashFiles to use frontend/src-tauri/gen/android/gradle/wrapper/gradle-wrapper.properties to change when Gradle wrapper cache is invalidated.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• OpenSecretCloud/Maple#308: Related workflow changes adding/standardizing sccache setup and tauri-cli version-gated install logic.
• revert(ci): undo Android parallel build workflow #396: Modifies Android CI/release workflows around Tauri CLI installation and caching, overlapping with these changes.
• Pin CI action and tool versions #523: Touches sccache download/verification and caching/configuration, closely related to this PR's sccache updates.

Poem

🐰 Bun cached snug, sccache set to spin,
Xcode ready early, ONNX warmed within,
Gradle keys tuned, caches shared with care,
CI hops lighter through the build-room air,
a rabbit cheers — swift runs everywhere!

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title 'Restore PR build cache parity' directly and specifically summarizes the main objective of the changeset, which is to restore missing PR build caches across multiple CI/CD workflows to match the signed build workflows.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch restore-pr-build-cache-parity

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View logs

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 4 additional findings.