docs(readme): add git-gate to architecture diagram

Bumps the sidecar count from two to up to three; the diagram and
bullet list now cover the git-gate alongside pipelock and ssh-gate,
including the ~/.gitconfig pushInsteadOf wiring that fires the
agent's git push through the gate.

README.md

@@ -56,12 +56,14 @@ pieces of v1.
 
 ## Architecture
 
-A bottle is three containers on a per-agent Docker `--internal`
-network. The agent has no default route off-box; its only way out is
-through the pipelock sidecar (for HTTP/HTTPS) or the ssh-gate sidecar
-(for SSH). Both sidecars also sit on an egress network that does have
-internet access, so the agent's traffic always passes through a
-container that enforces the manifest before it leaves the host.
+A bottle is the agent container plus up to three per-protocol egress
+sidecars on a per-agent Docker `--internal` network. The agent has no
+default route off-box; its only way out is through the pipelock
+sidecar (for HTTP/HTTPS), the ssh-gate sidecar (for SSH), or the
+git-gate sidecar (for `git push`). Each sidecar also sits on an
+egress network that does have internet access, so the agent's traffic
+always passes through a container that enforces the manifest before
+it leaves the host.
 
 ```
                             host  ( ./cli.py )
@@ -76,11 +78,17 @@ container that enforces the manifest before it leaves the host.
    │   │  built locally)  │                  │ (TLS bump, DLP,│  │     hosts
    │   │                  │                  │  allowlist)    │  │
    │   │ skills, env,     │                  └────────────────┘  │
-   │   │ ~/.ssh/config    │                                      │
-   │   │                  │   ssh            ┌────────────────┐  │  TCP to
+   │   │ ~/.ssh/config,   │                                      │
+   │   │ ~/.gitconfig     │   ssh            ┌────────────────┐  │  TCP to
    │   │                  │ ───────────────► │ socat/ssh image│──┼──►  bottle.ssh
    │   │                  │                  │ (alpine/socat, │  │     upstreams
    │   │                  │                  │  L4 forwarder) │  │
+   │   │                  │                  └────────────────┘  │
+   │   │                  │                                      │
+   │   │                  │   git push       ┌────────────────┐  │  SSH (push)
+   │   │                  │ ───────────────► │ git-gate image │──┼──►  to bottle.git
+   │   │                  │                  │ (gitleaks +    │  │     upstreams
+   │   │                  │                  │  git daemon)   │  │
    │   └──────────────────┘                  └────────────────┘  │
    │                                                             │
    │   agent on internal network (no default route);             │
@@ -90,7 +98,8 @@ container that enforces the manifest before it leaves the host.
 
 - **agent image** — built from the repo `Dockerfile` (`node:22-slim`
   base) on first run; runs `claude` with the manifest-granted skills,
-  env vars, and `~/.ssh/config`.
+  env vars, `~/.ssh/config`, and `~/.gitconfig` (the latter for the
+  git-gate's `pushInsteadOf` rules when `bottle.git` is set).
 - **pipelock image** — per-agent sidecar. Terminates the agent's
   outbound HTTP/HTTPS, enforces the resolved allowlist, runs DLP
   scanning. Design in `docs/prds/0001-per-agent-egress-proxy-via-pipelock.md`
@@ -99,9 +108,17 @@ container that enforces the manifest before it leaves the host.
   One container, one socat listener per `bottle.ssh` entry, each
   forwarding TCP to the upstream `Hostname:Port`. SSH does *not* go
   through pipelock. Design in `docs/prds/0007-ssh-egress-gate.md`.
+- **git-gate image** — per-agent sidecar built on `zricethezav/gitleaks`
+  (alpine + gitleaks + git-daemon + openssh-client). Runs
+  `git daemon --enable=receive-pack` so the agent can push to it
+  via `git://`; a pre-receive hook gitleaks-scans each incoming ref
+  and forwards clean refs to the real upstream over SSH using a
+  credential the agent never sees. Brought up only when `bottle.git`
+  has entries. Design in `docs/prds/0008-git-gate.md`.
 
-When the agent exits, `cli.py` tears down both sidecars and the two
-networks; nothing about a bottle persists between runs.
+When the agent exits, `cli.py` tears down every sidecar that was
+brought up and the two networks; nothing about a bottle persists
+between runs.
 
 ## Quickstart