fix(mcp): restore HTTP /mcp endpoint after 855 regression

855 deleted the HTTP /mcp route and pointed agents at ws://...crdt-sync,
but Claude Code's .mcp.json doesn't speak ws:// and the rendezvous WS
never had MCP method handlers wired up — so every spawned Claude Code
agent (gateway-routed and local) booted with zero huskies tools and
died on --permission-prompt-tool=mcp__huskies__prompt_permission.

Restore mcp_post_handler / mcp_get_handler / handle_initialize, re-add
the /mcp route, and revert all three .mcp.json writers to emit
http://localhost:{port}/mcp with explicit "type": "http". Reuses the
already-extracted gateway::jsonrpc types and the surviving
dispatch_tool_call / list_tools surfaces — net add ~140 lines.

Federation work is unaffected: /crdt-sync continues to do CRDT sync,
which is what it was actually doing. MCP-over-WebSocket for cross-LAN
agents was never wired up by 855 and can be done as a proper follow-up
with a regression test that boots a real claude and verifies tool
registration.

Verified end-to-end: /mcp initialize, tools/list (74 tools incl.
prompt_permission), and tools/call all respond correctly from inside
the rebuilt container.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/src/worktree/mod.rs

@@ -37,10 +37,10 @@ pub fn worktree_path(project_root: &Path, story_id: &str) -> PathBuf {
 }
 
 /// Write a `.mcp.json` file in the given directory pointing to the huskies
-/// rendezvous WebSocket endpoint at the given port.
+/// HTTP MCP endpoint at the given port.
 pub fn write_mcp_json(dir: &Path, port: u16) -> Result<(), String> {
     let content = format!(
-        "{{\n  \"mcpServers\": {{\n    \"huskies\": {{\n      \"url\": \"ws://localhost:{port}/crdt-sync\"\n    }}\n  }}\n}}\n"
+        "{{\n  \"mcpServers\": {{\n    \"huskies\": {{\n      \"type\": \"http\",\n      \"url\": \"http://localhost:{port}/mcp\"\n    }}\n  }}\n}}\n"
     );
     std::fs::write(dir.join(".mcp.json"), content).map_err(|e| format!("Write .mcp.json: {e}"))
 }
@@ -91,7 +91,7 @@ mod tests {
         let tmp = TempDir::new().unwrap();
         write_mcp_json(tmp.path(), 4242).unwrap();
         let content = std::fs::read_to_string(tmp.path().join(".mcp.json")).unwrap();
-        assert!(content.contains("ws://localhost:4242/crdt-sync"));
+        assert!(content.contains("http://localhost:4242/mcp"));
     }
 
     #[test]
@@ -99,7 +99,7 @@ mod tests {
         let tmp = TempDir::new().unwrap();
         write_mcp_json(tmp.path(), 3001).unwrap();
         let content = std::fs::read_to_string(tmp.path().join(".mcp.json")).unwrap();
-        assert!(content.contains("ws://localhost:3001/crdt-sync"));
+        assert!(content.contains("http://localhost:3001/mcp"));
     }
 
     #[test]