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-c0re/src/forge/mod.rs

@@ -17,9 +17,9 @@ pub use pr_merge::{
 };
 pub use reconcile::{reconcile_config_apply, reconcile_config_status};
 pub use repos::{
-    clone_config_into_proposed, create_agent_repo, ensure_config_repo, ensure_meta_remote,
-    ensure_repo, fast_forward_applied_main, fetch_config_main_into_applied, meta_read_access,
-    push_config, push_meta, shared_docs_access,
+    clone_config_into_proposed, ensure_config_repo, ensure_meta_remote, ensure_repo,
+    fast_forward_applied_main, fetch_config_main_into_applied, meta_read_access, push_config,
+    push_meta, shared_docs_access,
 };
 pub use users::core_token;
 
@@ -112,21 +112,6 @@ const SHARED_ORG: &str = "internal";
 /// The shared docs repo inside `SHARED_ORG`. Cloneable by every agent
 /// at `{forge_http_base()}/internal/docs.git`.
 const SHARED_DOCS_REPO: &str = "docs";
-/// Forgejo org that owns agent-created repos. Agents can't create
-/// repos with their own token (`max_repo_creation = 0`); instead hive-c0re
-/// creates them here and adds the requesting agent as a **write** member
-/// (not owner/admin). Because the org — not the agent — owns the repo,
-/// perms stay c0re-managed and branch protection (referencing
-/// [`OPERATORS_TEAM`]) can block the author from merging their own PR. This
-/// is the "agents namespace" repos land in by default. The swarm-controller
-/// ensures the org itself.
-const AGENTS_ORG: &str = "agents";
-/// Operator merge-gate team inside [`AGENTS_ORG`]. Provisioned **empty** by
-/// the swarm-controller (so perms can be set before anyone joins); the
-/// operator adds herself via the forge UI. Branch protection on agents-org
-/// repos references this team by name for the merge/approval whitelist, so
-/// the rule never hardcodes a specific reviewer agent (which may not exist).
-const OPERATORS_TEAM: &str = "operators";
 
 /// Leak `s` to get a `&'static str` warning `kind` for the small, bounded
 /// set of boot warnings in [`ensure_all`] keyed by a runtime name (at