chore(contract): record the complete message-output consumer set

[ss-o]

Summary

Records the three missing message-output consumers in
contracts/public-contract-v1.json and refreshes evidence_reviewed.

Closes #463

Problem

The manifest listed two consumers of the message-output surface. A direct
search of the organization finds five consumer files across two repositories.

The registry exists so a breaking change to a public surface can be scoped
cheaply and completely. e50d19e (feat!: rebuild message output with safe auto formatting, #457) changes the emitted byte stream of every message and is part
of the pending next to main promotion. Scoping it against the registry alone
would have covered two of five consumer files.

Change

Repository	Path	Evidence commit
z-shell/wiki	docs/guides/syntax/01_standard.mdx	3c56c281
z-shell/wiki	community/05_gallery/collection/03_programs.mdx	5f3450cb
z-shell/src	public/zsh/snippets/welcome.zsh	a715c1d0

z-shell/src was already listed for installer-git-output only. Its welcome
snippet is a separate dependency on message-output.

z-shell/z-a-meta-plugins/tests/prezto-meta-plugin.zsh defines a local stub
+zi-message() { :; }. That is a test double, not a consumer, and is
deliberately excluded.

Verification

Each path was fetched from the GitHub API at its proposed pin and confirmed to
contain the usage, rather than relying on a local checkout:

docs/guides/syntax/01_standard.mdx @ 3c56c281
    atinit'+zi-message "{bapo}Cloned!"'
    atclone'+zi-message "{quos}Boom!"'
    atload'+zi-message "{apo}Loaded!"'

community/05_gallery/collection/03_programs.mdx @ 5f3450cb
    atclone'+zi-message "{auto}Installing brew …"'

public/zsh/snippets/welcome.zsh @ a715c1d0
    +zi-message "{auto}\`Welcome to Zi :)\`"
    +zi-message "{hi}I am the snippet\!"

zsh scripts/public-contract-evidence.zsh reports all three new pins current.
zsh tests/public-contract-impact.zsh passes, including
consumer evidence must be complete and SHA-pinned and
evidence URLs must match their declared repository and path.
trunk check reports no issues.

Out of scope

The evidence detector reports five pre-existing stale pins unrelated to this
surface:

z-shell/docs/code/zsdoc/asciidoc/zi.zsh.adoc
z-shell/src/public/sh/install.sh
z-shell/src/public/zsh/init.zsh
z-shell/zd/tests/helpers.zsh
z-shell/z-a-meta-plugins/z-a-meta-plugins.plugin.zsh

A stale pin is a review signal, not automatically a contract break. Re-reading
each consumer and bumping its pin is separate work.