refactor(manifest): key git config by host

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

@@ -269,12 +269,14 @@ cred_proxy:
       token_ref: GITEA_TOKEN
       role: [git-insteadof, tea-login]
 git:
-  - Name: claude-bottle
-    Upstream: ssh://git@gitea.dideric.is:30009/didericis/claude-bottle.git
-    IdentityFile: ~/.ssh/gitea-delos-2.pem
-    ExtraHosts:
-      gitea.dideric.is: 100.78.141.42
-    KnownHostKey: ssh-rsa AAAAB3...
+  remotes:
+    gitea.dideric.is:
+      Name: claude-bottle
+      Upstream: ssh://git@gitea.dideric.is:30009/didericis/claude-bottle.git
+      IdentityFile: ~/.ssh/gitea-delos-2.pem
+      ExtraHosts:
+        gitea.dideric.is: 100.78.141.42
+      KnownHostKey: ssh-rsa AAAAB3...
 egress:
   allowlist:
     - example.com

docs/prds/0022-sandbox-escape-integration-test.md

@@ -191,9 +191,11 @@ egress:
     - host: api.anthropic.com
 
 git:
-  - Name: throwaway
-    Upstream: ssh://git@127.0.0.1:22/throwaway.git
-    IdentityFile: ~/.ssh/cb-test-key  # fixture key
+  remotes:
+    127.0.0.1:
+      Name: throwaway
+      Upstream: ssh://git@127.0.0.1:22/throwaway.git
+      IdentityFile: ~/.ssh/cb-test-key  # fixture key
 ---
 ```
 

docs/prds/0025-bottle-extends.md

@@ -105,23 +105,17 @@ overlay it. For each field on `Bottle`:
 | Field        | Type                  | Merge                                       |
 |--------------|-----------------------|---------------------------------------------|
 | `env`        | `Mapping[str, str]`   | dict merge, child wins on key collision     |
-| `git`        | `tuple[GitEntry,…]`   | full replace if child declares `git:`       |
-| `git_user`   | `GitUser`             | child overlay: child's non-empty fields win |
+| `git.user`   | `GitUser`             | child overlay: child's non-empty fields win |
+| `git.remotes`| `tuple[GitEntry,…]`   | dict merge by host, child wins              |
 | `egress`     | `EgressConfig`        | full replace if child declares `egress:`    |
 | `supervise`  | `bool`                | full replace if child declares `supervise:` |
 
-Why full-replace for the list-valued fields (`git[]`,
-`egress.routes[]`):
+Why full-replace for `egress.routes[]`:
 
 - **Ordering matters.** Egress route ordering is part of the
   match semantics (first matching host wins). Merging two
   ordered lists by name introduces "where does the child's route
   go?" ambiguity.
-- **Name collisions are ambiguous.** If parent has
-  `git: [{Name: foo, Upstream: A}]` and child has `git:
-  [{Name: foo, Upstream: B}]`, "merge" could mean override-B or
-  error-on-collision. Full-replace makes the operator's
-  intent explicit.
 - **Simpler precedence.** "Child declares X → X wins, full
   stop" is one sentence; partial merges need a table per list.
 
@@ -129,9 +123,15 @@ The `env` dict is the one exception because dict-merge has no
 ordering concern and dict-keyed overrides are the obvious user
 expectation. (Same model as shell `export` precedence.)
 
-The `git_user` dataclass-overlay (each non-empty field wins
-individually) is so a parent can declare `git_user.name` and a
-child can add just `git_user.email`. The default `GitUser()`
+`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.
+
+The `git.user` dataclass-overlay (each non-empty field wins
+individually) is so a parent can declare `git.user.name` and a
+child can add just `git.user.email`. The default `GitUser()`
 fields are empty strings, which are treated as "not set" for
 overlay purposes — same `is_empty()` predicate the provisioner
 uses.
@@ -191,7 +191,7 @@ moot because there's only one bottle source.
    - Implement `_merge(parent: Bottle, child_raw: dict, name: str)
      -> Bottle` with the rules table above.
    - Unit tests: simple two-bottle extends, env merge with
-     collision, list-replace for git + egress, git_user overlay,
+     collision, host-keyed git remote merge, egress list-replace, git.user overlay,
      supervise override, missing parent dies, cycle dies, deeper
      chains (A extends B extends C).
 3. **Docs.** Add an `extends:` example to the README's manifest