QVAC-22630 chore: bump model-fit to 0.2.1 and record the fit-context fix

[iancris]

🎯 What problem does this PR solve?

@qvac/model-fit 0.2.0 shipped the unresolved-fit-context fix from #3890 without
documenting it.

The ordering is what hid it: #3890 merged at 08:20, #3725 bumped the package to
0.2.0 at 11:06 as part of the qvac-fabric 10069.1.0 rollout, and npm published
0.2.0 at 11:39. The model-fit-v0.2.0 tag points at 917db3ce4, which contains
#3890's merge commit 02fcd711f — so the code is in the published tarball, while
the [0.2.0] changelog entry mentions only the fabric bump. Anyone reading the
changelog to find out when a zero-context SUCCESS stopped being possible finds
nothing.

📝 How does it solve it?

Patch-bumps to 0.2.1 and writes the entry the fix should have had, describing
the merged code:

• detail::finalizeFitContext reclassifies a successful fit whose context could
  not be resolved — fitted nCtx of 0 with no trained-context GGUF metadata — as
  ERROR / model-unreadable, instead of returning a SUCCESS carrying
  nCtx: 0 that a caller cannot replay.
• parseFitProcessResponse rejects a completed response with status: 0 and a
  non-positive nCtx, as defence in depth behind the native fix.

This release carries no source change. Because the fix already shipped inside
0.2.0, the diff is CHANGELOG.md plus the version field and nothing else, and
both the changelog entry and the commit body say so rather than letting 0.2.1
read as a new fix. The alternative was to append the block to the existing
[0.2.0] entry — addons get a git tag and no GitHub Release body, so nothing
published would have been contradicted — but a released version's notes are a
poor place to grow new content, and a dedicated entry leaves the ordering legible.

🧪 How was it tested?

• ## [0.2.1] matches the extractor's own regex at
  .github/actions/verify-changelog-notes/action.yml
  ($0 ~ "^## \\[" version "\\]"), and the section body is non-empty up to the
  next ^## [.
• package.json version equals the heading version exactly.
• git diff --stat origin/main shows exactly two files; git diff --check is
  clean.
• 0.2.0 confirmed as the current npm latest, so 0.2.1 is a real forward
  bump and not a re-publish.
• No build or test run: no source, build or manifest file is touched. vcpkg.json
  and vcpkg-configuration.json are deliberately untouched.

⚠️ Breaking changes

None. Version metadata and documentation only.

[github-actions]

Review Status

Current Status: ✅ APPROVED
Approvals so far: Team Lead: 1, Member: 1

[github-actions]

License compliance — clean

No new dependency license findings in this PR.

Warn-only (shadow) mode — this check does not block merges yet.

Updated automatically by the canonical license compliance workflow.

NOTICE presence (advisory)

Missing NOTICE (advisory, does not block):

• ./.github/actions/release-merge-guard
• ./docs/website
• ./packages/ggml-coload-smoke
• ./packages/fabric/test/integration
• ./packages/inference-addon-cpp/mobile
• ./packages/sdk/e2e
• ./packages/llm-llamacpp/benchmarks/performance
• ./packages/llm-llamacpp/benchmarks/server
• ./packages/vla-ggml/sim/server
• ./packages/embed-llamacpp/benchmarks/performance
• ./packages/embed-llamacpp/benchmarks/server
• ./packages/asr-ggml/benchmarks/server