Implement the harness contract and prove it against rein-aharness (GLAS-WP-0001-T02/T03/T04)

- src/glas_harness/contract.py: Rein ABC (start_session/dispatch_tool/
  end_session), SandboxHandle/ToolCall/ToolResult, per docs/harness-contract.md.
- reins/rein_aharness.py: adapter around the rein-aharness CLI. Collapses
  a whole `agent-harness run` into one dispatch_tool call for now (no
  per-tool hooks yet — tracked in rein-aharness HARNESS-WP-0002-T03);
  verifies success via new-commit detection, mirroring rein-aharness's
  own success signal.
- gateway.py + cli.py: resolves a sand-boxer sandbox, runs one task
  through a rein, tears the sandbox down.
- registry/reins/*.yaml (rein-aharness implemented, rein-openweights
  planned) and profiles/harness.agent-dev{,-local}.yaml, pairing with
  sand-boxer's profile.agent-dev and the new profile.bwrap-local.

Tested against a real local git repo + mocked SandboxManager/CLI
subprocess (10 tests, all passing). A real live run against the actual
Claude Code CLI is deliberately left for a human-triggered follow-up —
not executed autonomously since it spends real API credits/credentials.

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

pyproject.toml

@@ -0,0 +1,30 @@
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[project]
+name = "glas-harness"
+version = "0.1.0"
+description = "Meta-framework routing between concrete agent-harness backends (reins)"
+requires-python = ">=3.11"
+dependencies = [
+    "pydantic>=2.0",
+    "pyyaml>=6.0",
+]
+
+[project.scripts]
+glas-harness = "glas_harness.cli:main"
+
+[tool.uv.sources]
+sandboxer = { path = "../sand-boxer", editable = true }
+
+[project.optional-dependencies]
+sandbox = ["sandboxer"]
+dev = ["pytest>=8"]
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/glas_harness"]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+pythonpath = ["src"]