Record live distribution install evidence in the distribution docs (#511)

[amirbena]

Fixes #521

Sub-issue of #511, which stays open: Windows and Cursor cross-release update (tested install was commit-pinned) are still open. Parent: #506.

What

• Behavior / contracts: None

• Governance / policy: None

• Packaging / portability: docs/distribution.md records live installs (client, date, observed version 1.56.0) for skills.sh, Claude, Codex, Copilot and Cursor and marks them verified, separating install, discovery and runtime smoke results for Claude, Codex and Cursor (not review-quality validation); skills.sh update and listing stay documented. README gains a distribution install command. No adapter added; Codex installed through the existing marketplace file.

• Changelog: generated at release from the two lines below — never edit CHANGELOG.md (see docs/RELEASE.md)

• Release category: none

• Release entry:

• Guide restructure: docs/distribution.md is now the canonical install/update/verify guide (recommended managed install, per-consumer commands, per-consumer update semantics, install/discovery/runtime/update matrix, manual ZIP demoted to a fallback). README "Install" leads with the managed path and demotes packaging to "Manual / offline". Also fixes an earlier edit that had overwritten the Claude row of the install table.

Validation

• Relevant validation was run, or the reason it could not be run is stated.
• Installs run against the published amirbena/code-review-skills v1.56.0 in isolated config directories; validate-markdown-links.py passes.
• Cross-release v1.56.0 → v1.57.0 evidence for skills CLI, Claude, Codex and Cursor is recorded in the guide (see the Verify skills.sh and Agent Plugin consumer paths and document distribution install and update flows #511 comment).
• Cursor was verified manually (Cursor 3.17.8, invocation worked). Not run: Windows and a Cursor update on a refresh-capable install; Copilot update.

Review

Not reviewed.