fact-gate 1.2.0 — git pre-commit mode, sticky PR comment

Where it runs, part two: git and the PR conversation. Chosen after a second
round of adversarial review of the roadmap, which dropped an MCP server and
a browser playground (no evidence either channel produces users for a CI
tool) in favour of the two things every team already has.

Added

• fact-gate pre-commit. Checks the staged content (git show :path)
  of every file the nearest .fact-gate.json covers, refuses the commit on
  a contradiction. Editor-agnostic: Cursor, Codex, Copilot and humans go
  through the same gate. .pre-commit-hooks.yaml for the pre-commit
  framework; husky and lefthook one-liners in the README. checkStaged,
  stagedPaths, stagedContent in the library.
• Sticky PR comment. comment: 'true' on the Action posts one comment
  with the report and keeps it updated on every push (pull-requests: write).
  The Action now records its exit code and fails in a final step, so the
  comment is posted even when the gate blocks.
• fact-gate/core: the browser-safe half of the library (no Node built-ins).

Deferred, deliberately

MCP server, GitHub Pages playground, SARIF output, dedicated JUnit / lcov /
git-log adapters. The cmd measurement already covers any artefact a shell
can read; the rest will be built when a user asks.