docs(changelog): add missing 0.2.1 user-facing changes

[liugddx]

Summary

This follows up a post-merge review of #6077. It adds six user-facing changes that are missing from the curated 0.2.1 section of CHANGELOG.md, before asf-source-candidate.yml cuts RC1.

I compared the 0.2.1 section against every feat/fix/perf commit between v0.2.0-incubating-rc2 (54542021a) and #6077's merge base. All 40 PRs the section references are in range. The section is intentionally curated, so this adds only the omissions with a user, packager or upgrade impact:

• Changed:
  • fix(runtime-host): reject manual archive while WorkHub relationships are live #5957: manual archive is now refused while a WorkHub delegation or a live linked child still points at the task. This is a visible behaviour change.
• Fixed:
  • fix(deps): clear shipped-closure advisories (brace-expansion, fast-uri, axios) #5906: shipped dependencies are updated to clear published advisories (brace-expansion, fast-uri, axios). Packagers look for this.
  • fix(usage): record aborted auxiliary model calls as usage-unknown, not zero #5890: aborted or usage-less auxiliary calls are recorded as usage-unknown rather than zero. It pairs with the listed feat(usage): filter usage queries by model call kind #5709.
  • fix(runtime): stop shell commands when their Runtime Host dies #5986: shell commands now stop when their Runtime Host dies.
  • fix(runtime): keep the Anthropic cache breakpoint on replayed history #6041: Anthropic prompt caching keeps its breakpoint on replayed history.
  • fix(desktop,ui): stage a selected message's quotes on edit #5274: Desktop Edit & resend keeps quotes, while messages with attachments still refuse.

Nothing else changes. The 0.2.0 section and the upgrade notes are untouched, and 0.2.1 stays Unreleased.

Refs #6077

Verification

• git diff --check passes, and the ASF header is unchanged.
• No script parses CHANGELOG.md; desktop-nightly.test.mjs only has an unrelated fullChangelog option.
• Each entry's wording was checked against its merged PR description.

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Claude Code compared the changelog against the commit range and drafted the entries; I reviewed them against each PR.

Checklist

• Tests cover the change and fail without it. Not applicable: this is a documentation-only change.
• Lint, format, typecheck and the affected suites pass locally. Only the diff check applies.

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

🤖 Generated with Claude Code

[Astro-Han]

Automated review notice: This comment was posted by an automated review agent. It is not an independent human review and does not replace one.

I found no P0–P3 issue at 563fbae346ea1df0b65218e15de7f664f22a94a5.

The six new entries match their merged PRs (#5274, #5890, #5986, #6041, #5906, #5957). I checked that each merge commit is not contained in v0.2.0-incubating-rc2, so none of them already shipped in 0.2.0, and that none of the numbers already appears elsewhere in the changelog. The wording matches each PR's behavior, including the attachment limitation for Edit & resend in #5274 and the WorkHub archive refusal in #5957. The change is limited to CHANGELOG.md; CI is green and the branch merges cleanly with main.