fix(git-gate): review — sandbox naming, ResolverLike Protocol, token-required note

Addresses PR #365 review:
- Type `resolve_sandbox_root`'s resolver param as a `ResolverLike` Protocol
  (structural, `resolve_bottle_id` only) — fixes the pyright errors from
  passing a duck-typed fake resolver in tests; mirrors
  egress_addon_core.PolicyResolverLike.
- Rename `_project_root`/`project_root`/`resolve_repo_root`/
  `DEFAULT_PROJECT_ROOT` -> `_sandbox_root`/`sandbox_root`/
  `resolve_sandbox_root`/`DEFAULT_REPO_ROOT`: "sandbox" names the per-tenant
  scope; "project" was too amorphous. `GIT_PROJECT_ROOT` keeps git's own
  env-var name.
- Note the single-tenant path is transitional (stripped once every backend
  runs the consolidated gateway).
- policy_resolver: document that the optional identity token is
  transitional — the consolidated end state requires it (flips at the
  /resolve boundary once token *delivery* lands, a PRD 0070 open question).
- Split the long line in main() (was 105 cols).

pyright 0 errors; pylint 9.95/10; unit suite green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WBMWTEtQdJ4W5UrWuLHCck

bot_bottle/policy_resolver.py

@@ -73,8 +73,15 @@ class PolicyResolver:
     def resolve(self, source_ip: str, identity_token: str = "") -> str | None:
         """The calling bottle's policy blob, or None if unattributed. Always
         fetches from the orchestrator so revocations / changes / teardowns
-        are honored immediately. `identity_token` is optional — omit it to
-        resolve by source IP alone (the network-layer attribution).
+        are honored immediately.
+
+        `identity_token` is optional *transitionally* — omitting it resolves
+        by source IP alone (the network-layer attribution, sound by
+        construction on Firecracker's `/31`+nft, weaker elsewhere). The
+        consolidated end state makes the token mandatory so the app-layer
+        defense is always enforced, not silently degraded; that flips at the
+        `/resolve` boundary once identity-token *delivery* lands (a PRD 0070
+        open question — we can't require what the agent can't yet present).
         Raises `PolicyResolveError` if the orchestrator can't be reached."""
         payload = self._post_resolve(source_ip, identity_token)
         if payload is None: