fix(cred_proxy): close git-push bypass + route through pipelock (PRD 0010)

Three coupled fixes that close a documented bypass of git-gate's
gitleaks pre-receive hook:

1. cred-proxy refuses git smart-HTTP push at runtime. Any path
   ending in /git-receive-pack or /info/refs?service=git-receive-pack
   returns 403 with a pointer at the bottle.git SSH path. Fetch
   (upload-pack) is still allowed — the bypass we're closing is
   push, where gitleaks is the load-bearing scanner. Hard guarantee.

2. The provisioner suppresses the cred-proxy `~/.gitconfig` insteadOf
   rewrite for any host already declared in bottle.git. git-gate is
   the canonical git path there; we don't write a competing rule
   that would let `git clone https://<host>/...` succeed in ways
   that confuse on push. Defense in depth — (1) is the hard guarantee.

3. cred-proxy routes its outbound HTTPS through pipelock. The
   sidecar's environ now sets HTTPS_PROXY=<pipelock-url>, and the
   image's entrypoint runs `update-ca-certificates` over the
   per-bottle pipelock CA (docker cp'd into
   /usr/local/share/ca-certificates/pipelock.crt before start) so
   the proxy's HTTPS client trusts pipelock's bumped certs.

   Consequence: pipelock's allowlist + body scanner now sit in the
   cred-proxy egress path the same way they sit in front of direct
   agent traffic. The cred-proxy upstream hosts (api.github.com,
   github.com, gitea hosts, registry.npmjs.org) come OFF
   pipelock's passthrough_domains. Only api.anthropic.com remains
   on passthrough (LLM body content legitimately trips DLP).

PRD 0010 updated to reflect all three. Tests adjusted: the
"cred-proxy hosts go on passthrough" assertion in
test_pipelock_allowlist flips to "they don't", a new
TestIsGitPushRequest exercises the smart-HTTP refusal predicate,
and the gitconfig renderer tests cover the per-host suppression
matrix.

tests/unit/test_cred_proxy_server.py

@@ -7,6 +7,7 @@ from claude_bottle.cred_proxy_server import (
     Route,
     build_forward_headers,
     filter_response_headers,
+    is_git_push_request,
     load_tokens,
     parse_routes,
     select_route,
@@ -183,6 +184,49 @@ class TestFilterResponseHeaders(unittest.TestCase):
         self.assertNotIn("transfer-encoding", names)
 
 
+class TestIsGitPushRequest(unittest.TestCase):
+    """git push over HTTPS goes through /info/refs?service=git-receive-pack
+    (capabilities probe) then POST /git-receive-pack (the push body).
+    Fetches use /git-upload-pack and are not blocked — the bypass we're
+    closing is push, since git-gate's gitleaks pre-receive is the scanner
+    for outbound git data."""
+
+    def test_push_capabilities_probe_blocked(self):
+        self.assertTrue(is_git_push_request(
+            "/gh-git/owner/repo.git/info/refs",
+            "service=git-receive-pack",
+        ))
+
+    def test_push_body_blocked(self):
+        self.assertTrue(is_git_push_request(
+            "/gh-git/owner/repo.git/git-receive-pack", "",
+        ))
+
+    def test_fetch_capabilities_allowed(self):
+        self.assertFalse(is_git_push_request(
+            "/gh-git/owner/repo.git/info/refs",
+            "service=git-upload-pack",
+        ))
+
+    def test_fetch_body_allowed(self):
+        self.assertFalse(is_git_push_request(
+            "/gh-git/owner/repo.git/git-upload-pack", "",
+        ))
+
+    def test_rest_api_allowed(self):
+        # tea/gh-style REST calls hit /api/v1/... — unrelated.
+        self.assertFalse(is_git_push_request(
+            "/gitea/gitea.dideric.is/api/v1/repos/x/y", "",
+        ))
+
+    def test_push_with_extra_query_params(self):
+        # `service` may appear with other params in any order.
+        self.assertTrue(is_git_push_request(
+            "/gh-git/owner/repo.git/info/refs",
+            "trace=1&service=git-receive-pack",
+        ))
+
+
 class TestLoadTokens(unittest.TestCase):
     def test_reads_per_route_env(self):
         routes = (