Activate Stack CLI 0.5.2 across distribution channels

[konojunya]

Background

Stack CLI 0.5.2 is available from the immutable GitHub Release, crates.io, the owner-maintained Homebrew tap, and the owner Aqua registry. The full all-channel distribution smoke completed successfully for the published source before this activation update.

Implementation Approach

• Promote the documented current release and machine-readable availability contract from 0.5.1 to 0.5.2.
• Refresh the Aqua consumer fixture and checksum lock for all four supported native targets.
• Pin the merged Stack Docs revision and regenerate the installable stack-diagrams skill for published CLI 0.5.2.

Testing Approach

• Full 19-cell Direct, Aqua, Cargo, and Homebrew smoke: https://github.com/stack-sh/cli/actions/runs/34008827433
• Distribution contract, Aqua registry, publication completion, release security, and workflow guard tests.
• Four-target Aqua archive mapping plus native install, command, completion, and manual checks.
• Agent skill source synchronization and process-level CLI integration tests.
• Rust tests, Clippy, documentation, release build, package dry run, SVG validation, and pinned specification conformance.

Review Perspectives / Points of Concern

• This follow-up does not modify tags, release assets, or the publication-time release manifest.
• The distribution contract advances only after every supported channel passed clean-install verification.
• The Docs pin is immutable and its generated manifest SHA-256 is verified before skill synchronization.