feat(aur): add AUR packaging with auto-publish on release

[jamesbrink]

Summary

• Add three in-tree AUR packages — claudex-bin (repackages release tarball), claudex (builds from source tarball), claudex-git (tracks main HEAD). PKGBUILDs install bash/zsh/fish completions out of the box.
• Wire a publish-aur matrix job into release.yml that auto-refreshes pkgver + sha256sums and pushes to AUR on every tag push, gated on AUR_SSH_PRIVATE_KEY.
• Add a headless Arch container (packaging/aur/test/Dockerfile) and scripts/aur/test-in-docker.sh for local PKGBUILD smoke tests on non-Arch hosts.
• Teach claudex update to recognize pacman/AUR installs (/usr/bin/claudex, /usr/sbin/claudex) so it points at paru -Syu instead of attempting to overwrite a pacman-owned file. Addresses the one P1 from the Codex peer review.

Test plan

• ci-local green — 222 tests pass, fmt + clippy + build clean.
• Docker smoke test: claudex-bin 0.4.0-1 builds, installs via pacman, claudex --version runs.
• No $pkgdir / /tmp leaks in installed completion files (clap-dynamic argv[0] gotcha fixed by invoking via PATH).
• update-pkgbuild.sh populates real v0.4.0 SHA256s for both claudex-bin and claudex against the live GitHub release.
• makepkg --printsrcinfo parses all three PKGBUILDs cleanly → .SRCINFO seeds committed.
• release.yml parses; publish-aur job declared with correct needs, if, matrix.
• New InstallKind::Pacman tests cover /usr/bin/claudex + /usr/sbin/claudex on Linux, and the off-Linux fallback.
• Maintainer one-time bootstrap (post-merge): clone each AUR git repo and push the initial PKGBUILD + .SRCINFO. After that, CI takes over for -bin and the source package on the next tag push.

Notes

• claudex-git is intentionally excluded from the CI matrix — it tracks main HEAD and is hand-bumped only when the build recipe changes.
• AUR_SSH_PRIVATE_KEY is already set on the repo (maintainer's primary ed25519 key, registered with the AUR account).
• Peer-reviewed via codex review --base main (high reasoning); one P1 raised and addressed.

See packaging/aur/README.md for the full release flow and bootstrap.

[codecov]

Codecov Report

❌ Patch coverage is 95.45455% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 80.05%. Comparing base (ef374bc) to head (6419cf1).

Files with missing lines	Patch %	Lines
src/commands/update.rs	95.45%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #23      +/-   ##
==========================================
+ Coverage   80.00%   80.05%   +0.05%     
==========================================
  Files          24       24              
  Lines        6312     6334      +22     
==========================================
+ Hits         5050     5071      +21     
- Misses       1262     1263       +1     

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[Copilot]

Pull request overview

Adds Arch User Repository (AUR) packaging for claudex with three packages — claudex-bin (binary), claudex (source), and claudex-git (VCS) — plus CI automation to auto-publish PKGBUILDs to the AUR on tagged releases. Also teaches claudex update to recognize pacman-managed install paths so it points users at paru -Syu instead of attempting to overwrite a package-owned file.

Changes:

• Add three in-tree AUR PKGBUILDs + .SRCINFO seeds under packaging/aur/, with a headless Arch Docker test harness and an update-pkgbuild.sh helper that refreshes pkgver + sha256sums.
• Wire a publish-aur matrix job into release.yml (gated on AUR_SSH_PRIVATE_KEY) that uses KSXGitHub/github-actions-deploy-aur to push to the AUR on every v* tag.
• Add InstallKind::Pacman to claudex update, classify /usr/bin/claudex and /usr/sbin/claudex as pacman-managed on Linux, surface a paru/yay/pacman hint, and update docs/README/CHANGELOG/CLAUDE.md accordingly.

Reviewed changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/commands/update.rs	Adds Pacman install kind, Linux-only /usr/bin + /usr/sbin detection, upgrade hint, and tests.
src/main.rs	Extends update --help text to mention pacman/AUR.
tests/cli_tests.rs	Asserts pacman appears in update help output.
packaging/aur/claudex-bin/PKGBUILD + .SRCINFO	Binary AUR package using release tarballs.
packaging/aur/claudex/PKGBUILD + .SRCINFO	Source-build AUR package from release tarball with cargo --frozen.
packaging/aur/claudex-git/PKGBUILD + .SRCINFO	VCS package tracking main, with conventional git describe pkgver.
packaging/aur/README.md	Documents release flow, bootstrap, and local smoke-test workflow.
packaging/aur/test/Dockerfile	Headless Arch container for makepkg smoke tests on non-Arch hosts.
packaging/aur/.gitignore	Ignores makepkg build artifacts.
scripts/aur/update-pkgbuild.sh	Rewrites pkgver/sha256sums against a release tag; portable across GNU/BSD sed and sha256sum/shasum.
scripts/aur/test-in-docker.sh	Driver for the Arch container smoke test (docker/podman, --rebuild/--shell flags).
.github/workflows/release.yml	Adds publish-aur matrix job gated on AUR_SSH_PRIVATE_KEY.
README.md, website/guide/installation.md, CHANGELOG.md, CLAUDE.md	Documentation updates covering the new install path and release-process invariants.

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