CI paths: Python Typecheck — add self-trigger path #844

Part of #834. Phase 1 (unanchored corrections — no dependency on any other slice).

What

python-typecheck.yml does not name its own file in paths:, so editing the workflow does not run it. Spec row 16.

Exact change

.github/workflows/python-typecheck.yml — replace the on: block with:

on:
  push:
    branches: [main]
    paths:
      - 'packages/python/**/*.py'
      - 'packages/python/**/*.pyi'
      - 'packages/python/pyproject.toml'
      - '.github/workflows/python-typecheck.yml'
  pull_request:
    paths:
      - 'packages/python/**/*.py'
      - 'packages/python/**/*.pyi'
      - 'packages/python/pyproject.toml'
      - '.github/workflows/python-typecheck.yml'

Only the two paths: lists change.

Expected checks on this PR

Files touched: .github/workflows/python-typecheck.yml only.

MUST run

• Python Typecheck

MUST NOT run

• Python Test, TS Test, Rust Test, Plugins Test, Python Lint, TS Lint, TS Typecheck

May still run (not yet filtered)

• Conventions (all 8 lanes), Release Precheck, Release Config Check, Changelog Check

Acceptance

• The PR's check list matches the three groups above exactly
• Mergify Merge Protections green
• Merge, close this issue

Notes

• No changelog fragment, no e2e attestation.
• Not anchored in .mergify.yml; independent of every other slice.