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_provision_cred_proxy.py

@@ -83,6 +83,40 @@ class TestRenderGitconfig(unittest.TestCase):
         self.assertIn("gitea.dideric.is/", out)
         self.assertIn("gitea.example.com/", out)
 
+    def test_github_suppressed_when_git_gate_covers_host(self):
+        # When bottle.git brokers github.com over SSH, git-gate is the
+        # canonical git path. The cred-proxy https://github.com/
+        # rewrite would let the agent push over HTTPS — bypassing
+        # gitleaks. Suppress it.
+        out = render_cred_proxy_gitconfig(
+            _upstreams([{"Kind": "github", "TokenRef": "GH"}]),
+            {"github.com"},
+        )
+        self.assertEqual("", out)
+
+    def test_gitea_suppressed_when_git_gate_covers_host(self):
+        out = render_cred_proxy_gitconfig(
+            _upstreams([{"Kind": "gitea", "TokenRef": "T",
+                         "Url": "https://gitea.dideric.is"}]),
+            {"gitea.dideric.is"},
+        )
+        self.assertEqual("", out)
+
+    def test_partial_suppression_keeps_other_giteas(self):
+        # Two gitea instances; git-gate brokers one. The other still
+        # gets the cred-proxy rewrite.
+        out = render_cred_proxy_gitconfig(
+            _upstreams([
+                {"Kind": "gitea", "TokenRef": "T1",
+                 "Url": "https://gitea.dideric.is"},
+                {"Kind": "gitea", "TokenRef": "T2",
+                 "Url": "https://gitea.example.com"},
+            ]),
+            {"gitea.dideric.is"},
+        )
+        self.assertNotIn("gitea.dideric.is/", out)
+        self.assertIn("gitea.example.com/", out)
+
 
 class TestRenderTeaConfig(unittest.TestCase):
     def test_empty_when_no_gitea(self):