feat: publish Arch Linux package repository

[zzwong]

Summary

• ingest package-specific .pkg.tar.zst release assets
• sign Arch packages and generate per-architecture pacman databases
• serialize package ingestion to prevent concurrent metadata push races
• remove superseded Arch package versions with repo-add --remove
• document repository key trust and pacman configuration

This is the distribution-side companion to open-cli-collective/google-cli#25.

Validation

• parsed both workflow files as YAML
• actionlint .github/workflows/*.yml
• local smoke test covering .PKGINFO architecture detection, package signing, and signed repo-add metadata
• git diff --check

Follow-up

After this merges, publish a Google CLI release containing the new Arch artifacts and verify installation from the GitHub Pages pacman repository.

[open-cli-zzwong]

Automated PR Review

Reviewed commit: 009f9f3c260e
Profile: default - Posting as: open-cli-zzwong[bot]

Summary

Reviewer	Findings
packaging:linux-repo-integrity	0

Reviewer Coverage

• packaging:linux-repo-integrity — complete (constrained); skipped: none; constraints: Review limited to repository integrity and publishing safety in the assigned changed workflow and README.

Inspected files (2)

• .github/workflows/receive-package.yml
• README.md

0 PR discussion threads considered. 0 summarized; 0 resolved.

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Completed in 5m 35s | $0.02 | openai-codex/gpt-5.6-terra | cr 0.10.299

Field	Value
Model	openai-codex/gpt-5.6-terra
Reviewers	packaging:linux-repo-integrity
Engine	pi_rpc · openai-codex/gpt-5.6-terra
Reviewed by	cr · open-cli-zzwong[bot]
Duration	5m 35s wall · 29s compute
Cost	$0.02
Tokens	9.1k in / 555 out

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