remove the create_repo agent tool

mara ruled on #4849 (c88934): "remove create_repo tool". The tool ran in
hive-c0re with the hive's core token, so it only ever worked for agents
on the hive that runs the forge.

Removed:

- the create_repo MCP tool and CreateRepoArgs (hive-agent-mcp)
- wire variants Request::CreateRepo and Response::RepoCreated
  (hive-core-agent-sock)
- hive-c0re's handle_create_repo, its valid_repo_name check and the
  dispatch arm
- forge::create_agent_repo and apply_operator_branch_protection, which
  had no other caller, plus AGENTS_ORG and OPERATORS_TEAM, whose only
  users they were
- the tool's docs (docs/tools/forge.md repo management, docs/turn-loop/
  mcp.md, the conventions tool-group table) and the doc comments that
  named it (hive-sock-client's response timeout, ensure_repo_creation_
  disabled, the security doc's merge-gate bullet)

ToolGroup::Forge is kept with no tools, the same way b88a5b24 kept
Lifecycle, so existing meta/capabilities.json grants still parse.

Forge state is untouched: existing agents/* repos keep their collaborators
and operators-team branch protection. The swarm-controller's own
create_repo (config-org repos) is a different path and is unchanged.

Closes #4849

hive-sock-client/src/lib.rs

@@ -51,9 +51,7 @@ const CONNECT_TIMEOUT: Duration = Duration::from_secs(5);
 /// that has not drained one JSON line in this long has stopped reading.
 const WRITE_TIMEOUT: Duration = Duration::from_secs(10);
 
-/// Response deadline for every call that does not pass its own. Sized for
-/// the slowest non-polling verb: `CreateRepo`, which makes several
-/// sequential forge API calls in hive-c0re before it answers.
+/// Response deadline for every call that does not pass its own.
 const DEFAULT_RESPONSE_TIMEOUT: Duration = Duration::from_mins(1);
 
 /// What to do when a connect or I/O attempt fails.