fix(macos): review fixes — token on plan, self-heal, symmetric digest, DHCP poll

Addresses findings from a high-effort review of the PRD 0070 macOS backend.

Correctness:
- Stamp identity_token onto MacosContainerBottlePlan after registration. git's
  gitconfig extraHeader and the supervise MCP --header read
  getattr(plan,"identity_token","") at provision time, and both reach the
  gateway on NO_PROXY (bypassing the egress proxy that carries the token). The
  plan never carried it, so /resolve fail-closed and every git fetch/push and
  supervise call from a macOS bottle would have been denied. Registration
  precedes provision(), so — unlike the run-time env — the plan can carry it.
- Self-heal the orchestrator: recreate when it is not (source-current AND
  answering /health), not on the source-hash label alone. A container running
  current code but with a wedged HTTP server was left alone and polled to
  death, failing every launch until manual deletion.
- image_digest and container_image_digest now read the same descriptor.digest
  field; dropped image_digest's id/tag fallback that could yield a value the
  container side can't produce — a permanent mismatch would have recreated the
  shared gateway on every launch (severing every live bottle's egress, since
  the replacement gets a new DHCP address).
- Poll for the agent's and gateway's DHCP address instead of a fatal read
  right after `container run` (there is no --ip; the address can lag start).

Cleanup:
- One _inspect_first + _descriptor_digest behind the four inspect readers.
- Shared bind_mount_spec (util) and host_db_dir (paths) replace per-module
  copies; _GIT_HTTP_PORT now imports git_http_backend.DEFAULT_PORT.
- Drop the dead _url cache / url property and the write-only agent_proxy_url.

Deferred (noted on the PR, not fixed here): the gateway image rebuilding on
every launch (needs source-hash-labeled build), SQLite shared across VM
guests, and the sh -lc profile-override edge — each is design-level or
behavior-risk beyond a review fix.

Verified: real Apple Container bring-up is green and idempotent; 1826 unit
tests pass with `container` absent (CI parity), pyright clean, pylint 9.86.

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

tests/unit/test_macos_container_launch_wiring.py

@@ -158,6 +158,36 @@ class TestIdentityTokenDelivery(unittest.TestCase):
         argv = bottle.agent_argv(["--help"], tty=False)
         self.assertNotIn("--env", argv)
 
+
+class TestPlanIdentityToken(unittest.TestCase):
+    """git-gate's gitconfig extraHeader and the supervise MCP --header read
+    `getattr(plan, "identity_token", "")` at provision time and both bypass the
+    egress proxy (NO_PROXY), so the exec-time proxy token never reaches them —
+    the plan must carry the token or /resolve fail-closes and git + supervise
+    are denied on macOS."""
+
+    def test_macos_plan_has_the_identity_token_field(self) -> None:
+        from dataclasses import fields
+
+        from bot_bottle.backend.macos_container.bottle_plan import (
+            MacosContainerBottlePlan,
+        )
+        names = {f.name for f in fields(MacosContainerBottlePlan)}
+        self.assertIn("identity_token", names)
+
+    def test_matches_the_docker_plan(self) -> None:
+        """Both consolidated backends must expose identity_token so a shared
+        provision-time consumer degrades to neither backend silently."""
+        from dataclasses import fields
+
+        from bot_bottle.backend.docker.bottle_plan import DockerBottlePlan
+        from bot_bottle.backend.macos_container.bottle_plan import (
+            MacosContainerBottlePlan,
+        )
+        docker = {f.name for f in fields(DockerBottlePlan)}
+        macos = {f.name for f in fields(MacosContainerBottlePlan)}
+        self.assertIn("identity_token", docker & macos)
+
     def test_provisioning_exec_also_carries_the_token(self) -> None:
         """`provision` runs through `exec`; a provider whose provision step
         fetches anything would otherwise egress token-less and be denied."""