[moriyoshi]

Summary

The v0.9.0 GitHub Release was created and published by hand shortly before the tag was pushed. Under immutable releases that froze it with no assets, so when release run 34788914182 finished building all five targets, the publish job refused at its preflight. The archives were recovered from the run's workflow artifacts and published under the companion tag dist-v0.9.0 on the same commit. The binaries in them are byte-identical to the ones in ghcr.io/moriyoshi/imbh:0.9.0.

This PR only changes docs:

• README.md: says 0.9.0's archives live at dist-v0.9.0 (set BASE=…/download/dist-v0.9.0 in the download recipe). Adds a ⚠️ to the Releasing section: never create a published Release for a version tag ahead of CD. If one has to exist early, leave it as a draft, which release.yml already reuses.
• CHANGELOG.md: adds a note at the top of [0.9.0] pointing to the companion tag.
• .agents/docs/TODO.md: closes the "v0.9.0 is prepared but not cut" item.
• .agents/docs/JOURNAL.md: appends an entry on how it happened, why recovery depended on the 90-day artifact retention, and why the tag is named dist-v0.9.0 and not v0.9.0-dist. A v* name would trigger release.yml and fall under the Version tags ruleset, and semver would sort it as a pre-release.

release.yml is unchanged. The failure happened outside the pipeline.

Test plan

• Docs only, no Rust or workflow changes, so the cargo gate doesn't apply
• The dist-v0.9.0 links resolve, and the download recipe works with the overridden BASE

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