feat: fold bot-bottle-orchestrator into bot_bottle/orchestrator subpackage

Moves the orchestrator into bot_bottle/orchestrator/ so one install gets
everything. Entry point is now `python -m bot_bottle.orchestrator run`.

- Add bot_bottle/orchestrator/ with all 14 modules (verbatim move; internal
  imports were already relative, so no changes inside orchestrator modules)
- Rewrite bootstrap.py: remove the lazy bot_bottle import guard, use direct
  relative imports from ..contrib.*
- Add bot_bottle/contrib/forge/base.py: ScopedForge (read-anywhere / write-scoped)
- Add bot_bottle/contrib/gitea/client.py: GiteaClient + GiteaForge (urllib.request only)
- Add bot_bottle/contrib/gitea/forge_state.py: ForgeState + SqliteForgeStateStore
- Add tests/unit/orchestrator/ (82 tests: 63 migrated + 19 new for contrib modules)

Closes #321

tests/unit/orchestrator/test_runner.py

@@ -0,0 +1,65 @@
+"""Unit: SubprocessBottleRunner + slugify (injected run fn)."""
+
+from __future__ import annotations
+
+import unittest
+from collections.abc import Sequence
+
+from bot_bottle.orchestrator.runner import SubprocessBottleRunner, slugify
+
+
+class SlugifyTest(unittest.TestCase):
+    def test_basic(self):
+        self.assertEqual("impl-didericis-bot-bottle-17",
+                         slugify("impl-didericis-bot-bottle-17"))
+
+    def test_collapses_and_strips(self):
+        self.assertEqual("a-b-c", slugify("  A_B/C!! "))
+
+
+class SubprocessRunnerTest(unittest.TestCase):
+    def setUp(self):
+        self.argvs: list[list[str]] = []
+        self.envs: list[dict[str, str]] = []
+
+        def fake_run(argv: Sequence[str], env: dict[str, str]) -> int:
+            self.argvs.append(list(argv))
+            self.envs.append(dict(env))
+            return 0
+
+        self.runner = SubprocessBottleRunner(
+            cli="/x/cli.py", base_env={"PATH": "/bin"}, python="/py", run=fake_run
+        )
+
+    def test_start_argv_and_env(self):
+        result = self.runner.start(
+            agent="impl", bottles=["claude", "dev"], label="impl-r-17",
+            prompt="do it", forge_env={"FORGE_OWNER": "didericis"},
+        )
+        self.assertEqual("impl-r-17", result.slug)
+        argv = self.argvs[0]
+        self.assertEqual(["/py", "/x/cli.py", "start", "impl", "--headless",
+                          "--label", "impl-r-17", "--prompt", "do it",
+                          "--bottle", "claude", "--bottle", "dev"], argv)
+        # forge_env merged over base_env for the child.
+        self.assertEqual("didericis", self.envs[0]["FORGE_OWNER"])
+        self.assertEqual("/bin", self.envs[0]["PATH"])
+
+    def test_start_no_bottles_omits_flag(self):
+        self.runner.start(agent="impl", bottles=[], label="l", prompt="p", forge_env={})
+        self.assertNotIn("--bottle", self.argvs[0])
+
+    def test_freeze_calls_commit(self):
+        self.runner.freeze("slug-1")
+        self.assertEqual(["/py", "/x/cli.py", "commit", "slug-1"], self.argvs[0])
+
+    def test_resume_headless(self):
+        r = self.runner.resume("slug-1", "address review")
+        self.assertEqual("slug-1", r.slug)
+        self.assertEqual(
+            ["/py", "/x/cli.py", "resume", "slug-1", "--headless", "--prompt",
+             "address review"], self.argvs[0])
+
+
+if __name__ == "__main__":
+    unittest.main()