docs: drop ssh from README/example, supersede PRD 0007 (PRD 0009)

- README architecture diagram drops the socat/ssh image box and
  the agent's ~/.ssh/config; the prose-bullets section drops the
  ssh image; the manifest example swaps `ssh:` for `git:` so
  someone copy-pasting it picks up the new shape.
- claude-bottle.example.json: `default` bottle's `"ssh": []` is
  gone (now just an empty bottle); the gitea-dev example already
  uses `git:` since the ExtraHosts work.
- PRD 0007 carries a "Superseded by PRD 0009" header at the top
  with a one-paragraph block explaining why; the file stays so
  the rationale of the prior design is still in-tree.
- git_gate.py: drop the now-stale shadow-route mention from a
  docstring (the validator went away in the manifest layer).

docs/prds/0007-ssh-egress-gate.md

@@ -1,9 +1,16 @@
 # PRD 0007: SSH egress gate
 
-- **Status:** Draft
+- **Status:** Superseded by PRD 0009 (2026-05-13)
 - **Author:** didericis
 - **Created:** 2026-05-12
 
+> **Superseded.** The ssh-gate sidecar and `bottle.ssh` manifest field
+> described below were removed in PRD 0009. Every upstream this PRD
+> targeted has since been folded into PRD 0008's git-gate, which
+> covers the same use case with credential isolation and gitleaks
+> scanning instead of bare L4 forwarding. Kept in-tree for the
+> history of intent.
+
 ## Summary
 
 Per-agent TCP-forwarder sidecar built from `bottle.ssh` entries; SSH stops