feat(git-gate): remove git remote host override plumbing

docs/prds/0008-git-gate.md

@@ -83,12 +83,7 @@ for a declared upstream:
 - **Manifest field.** `bottle.git` — a list of git remotes the
   bottle is allowed to talk to, each with the credential the gate
   uses to push upstream. The agent gets no parallel `bottle.ssh`
-  entry for those upstreams. Each entry may also carry an
-  `ExtraHosts: { hostname: ip }` map, surfaced to the gate as
-  `--add-host` so the gate can resolve upstreams whose public DNS
-  doesn't point at the reachable IP (e.g. Tailscale-only hosts).
-  The agent-side `insteadOf` rewrite keys off the original hostname,
-  so the manifest's `Upstream` URL stays human-readable.
+  entry for those upstreams.
 - **Agent-side URL rewrite.** Provisioner emits `~/.gitconfig`
   with `[url "<gate-url>"] insteadOf = <real-url>` so every git
   operation against the declared upstream (push, fetch, clone,

docs/prds/0009-remove-ssh-gate.md

@@ -88,8 +88,7 @@ the unused path.
 - **Pipelock interaction.** Drop the SSH-derived branch from
   pipelock's `ssrf.ip_allowlist` build. With no `bottle.ssh`
   there is no per-upstream IP carve-out to render; git-gate
-  has its own egress network and pulls in upstream resolution
-  via `ExtraHosts` plus DNS.
+  has its own egress network.
 - **Tests.** Delete the ssh-gate unit + integration suites,
   the ssh fixtures in `tests/fixtures.py`, and the
   shadow-route assertions in `test_manifest_git.py`. Adjust

docs/prds/0011-per-file-md-manifest.md

@@ -274,8 +274,6 @@ git:
       Name: bot-bottle
       Upstream: ssh://git@gitea.dideric.is:30009/didericis/bot-bottle.git
       IdentityFile: ~/.ssh/gitea-delos-2.pem
-      ExtraHosts:
-        gitea.dideric.is: 100.78.141.42
       KnownHostKey: ssh-rsa AAAAB3...
 egress:
   allowlist:

docs/prds/0025-bottle-extends.md

@@ -161,8 +161,7 @@ expectation. (Same model as shell `export` precedence.)
 `git.remotes` is also keyed, so it follows dict-style inheritance:
 children can override one host without restating every remote. The
 remote entry is replaced as a whole on host collision because
-`Upstream`, `IdentityFile`, `KnownHostKey`, and `ExtraHosts` are
-tightly coupled.
+`Upstream`, `IdentityFile`, and `KnownHostKey` are tightly coupled.
 
 The `git.user` dataclass-overlay (each non-empty field wins
 individually) is so a parent can declare `git.user.name` and a