feat(gateway): mandatory identity-token attribution on every data plane (PR #354 review)

Codex review: the /31 TAP doesn't make source IP unspoofable, and the
app-layer token was returned by launch but never delivered or enforced, so
a spoofed source could select a victim bottle's policy/tokens. Make the
token mandatory and deliver it on each attributed plane (anti-spoof landed
separately as the network boundary).

Enforcement (control plane):
- `Orchestrator.resolve` now requires a matching (source_ip, identity_token)
  pair (constant-time) — no source-IP-only fallback. `/resolve` fail-closes
  (403) on a missing/empty/mismatched token.

Delivery, per plane (the token is `token_urlsafe`, safe in a URL):
- egress: proxy credentials (`HTTPS_PROXY=http://bottle:<token>@gw`). The
  addon reads `Proxy-Authorization` — from the request (HTTP) or captured at
  the CONNECT for HTTPS tunnels (keyed by client conn, cleared on disconnect)
  — validates, and strips it (+ the legacy header) before upstream.
- git-http: a URL-scoped `http.<gate>/.extraHeader: x-bot-bottle-identity`
  in the agent's git config (only over the http transport).
- supervise: `mcp add --header x-bot-bottle-identity: <token>` (claude +
  codex); the server reads the header and passes it to resolve.

Wiring: thread `ctx.identity_token` onto the firecracker + docker plans and
into the agent env/config at launch.

Verified on a KVM host: egress with the correct proxy-cred token returns
200 (HTTP and HTTPS/CONNECT), and no-token / wrong-token return 403; a real
`cli.py start --backend=firecracker` launch provisions git config + the
supervise MCP header and reaches the agent session, all under mandatory
enforcement. Fixed a `claude mcp add` arg-order bug (--header must follow
the positional name/url) found by that launch.

Transparent proxy for tools that ignore proxy env is deferred to a
follow-up (see thread); anti-spoof + host firewall remain the fail-closed
boundary.

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

bot_bottle/supervise_server.py

@@ -65,6 +65,8 @@ except ModuleNotFoundError:
 
 
 MCP_PROTOCOL_VERSION = "2024-11-05"
+# App-layer identity token header (mirrors egress_addon / git_http_backend).
+IDENTITY_HEADER = "x-bot-bottle-identity"
 SERVER_NAME = "bot-bottle-supervise"
 SERVER_VERSION = "0.1.0"
 
@@ -541,8 +543,13 @@ class MCPHandler(http.server.BaseHTTPRequestHandler):
         resolver = getattr(self.server, "policy_resolver", None)
         if resolver is None:
             return config
+        # The agent's MCP client sends the identity token as a request header
+        # (provisioned via `mcp add --header`); the orchestrator requires the
+        # (source_ip, token) pair, so a missing/wrong token fail-closes below.
+        headers = getattr(self, "headers", None)
+        token = headers.get(IDENTITY_HEADER, "") if headers is not None else ""
         try:
-            bottle_id = resolver.resolve_bottle_id(self.client_address[0])
+            bottle_id = resolver.resolve_bottle_id(self.client_address[0], token)
         except PolicyResolveError as e:
             raise _RpcInternalError(f"orchestrator unreachable, cannot attribute: {e}") from e
         if not bottle_id: