chore: adopt trunk-based development

Closes #27.

PROJECT.md
- Git section: TBD as the convention. Commit to main, one logical
  change per commit, `task check` locally before push, CI is the
  quality gate. PRs only for the parallel-agent exception.
- Agent rule 6: rewritten to match.

.gitea/workflows/cd.yml
- Drop the pull_request trigger — vestigial under TBD.
- Drop the `if: github.event_name != 'pull_request'` guard on the
  build job (now always true since pull_request no longer fires).
  Tag pushes still build (no version gating regression).
- Deploy `if` left alone — already correctly limits deploy to
  main pushes, skipping tag-push builds.

.githooks/pre-push (new)
- Runs `task check` before every push. Set up via `task setup:hooks`,
  which sets core.hooksPath to the in-repo .githooks dir.

Taskfile.yml
- New `setup:hooks` task to install the pre-push hook on a fresh
  clone.

README.md
- Quickstart section showing `task setup:hooks` + the TBD policy.

Derived adapters regenerated via `task context:sync` and committed
in the same commit (single-commit invariant).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.githooks/pre-push

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+set -euo pipefail
+echo "→ Running task check before push..."
+task check
+echo "✓ pre-push check passed"