ci+chore: PEP 740 attestations via astral-sh/attest-action; middleware 0.0.3

Restores what #873 traded away, without reintroducing the toolchain skew.
uv publish UPLOADS attestation files found beside the dists by default
(--no-attestations is the opt-out) — it just doesn't MINT them. Astral's
own publishing example pairs it with astral-sh/attest-action for exactly
that. One toolchain end to end, attestations back.

- attest step gated to the real release (a dry run uploads nothing for
  attestations to accompany); SHA pin f589a42a verified against tag v0.0.6
  (lightweight tag, commit direct); the action's input is  (glob) —
  caught by reading action.yml at the pinned SHA, not the README
- middleware bumped to 0.0.3: attestations are only provable on a fresh
  upload, and PyPI versions are immutable. No code change; consumers pin
  >=0.0.2 and are unaffected. The 0.0.3 upload doubles as the verification
  (simple-API provenance must flip from 'none')

Verified locally: 0.0.2 artifacts pass current twine check (Metadata 2.5),
YAML parses.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: blove

.github/workflows/publish-middleware-python.yml

@@ -76,6 +76,17 @@ jobs:
         working-directory: packages/threadplane-middleware
         run: uv publish --dry-run dist/*
 
+      # PEP 740 attestations: `uv publish` uploads attestation files found
+      # next to the dists (on by default) but does not mint them — Astral's
+      # own publishing example pairs it with their attest-action for exactly
+      # this. Generated for the real release only; a dry run uploads nothing
+      # for them to accompany. SHA pin verified against tag v0.0.6.
+      - name: Generate PEP 740 attestations
+        if: ${{ inputs.dry_run == false }}
+        uses: astral-sh/attest-action@f589a42a7efb6fe400b4f400de60b4bc90390027 # v0.0.6
+        with:
+          paths: packages/threadplane-middleware/dist/*
+
       # uv publish, not the pypa action: the pinned action image's twine
       # rejected the Metadata-Version 2.5 that current `uv build` emits
       # ("InvalidDistribution: '2.5' is not a valid metadata version"), while

packages/threadplane-middleware/pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "threadplane-middleware"
-version = "0.0.2"
+version = "0.0.3"
 description = "LangGraph middleware for binding client-declared tool stubs and routing client tool calls to END so the browser executes them."
 readme = "README.md"
 license = { text = "MIT" }