refactor(mcp): connect Claude Code via direct HTTP, remove stdio bridge

Claude Code now supports MCP servers over HTTP natively (type: "http"
in .mcp.json). The stdio↔HTTP bridge binary was a workaround for the
older stdio-only constraint and is no longer needed — the supervisor
NodePort on koala (30320) is reachable over Tailscale from any client
machine.

Removed:
- cmd/bridge/ (Go source, ~60 lines)
- bin/supervisor-bridge artifact
- Taskfile bridge:build target and the build aggregate's reference
- README "Build the bridge binary" instruction

Updated:
- .mcp.json switched to {type:"http", url:"http://koala:30320/mcp"}
- README architecture diagram and "Connect a project" section

Behavioural prerequisite for this change shipped in 7f7524c
(notifications fix). Verified end-to-end: tier tool call returns
{tier:2, label:"lan-only"} via direct HTTP, no shim.

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

README.md

@@ -10,10 +10,10 @@ into a searchable brain.
 ```
 Your Claude Code session (in any project)
     │
-    │  MCP tools (over stdio bridge → HTTP)
+    │  MCP over HTTP (Tailscale)
     ▼
-supervisor  :3200   — skill workers: tdd, retrospective
-ingestion   :3300   — brain HTTP API: query wiki, write notes
+supervisor  :3200 (NodePort 30320 on koala) — skill workers: tdd, retrospective
+ingestion   :3300                            — brain HTTP API: query wiki, write notes
     │
     ▼
 brain/
@@ -55,18 +55,18 @@ Create `.mcp.json` in your project root:
 {
   "mcpServers": {
     "supervisor": {
-      "command": "/Users/mathias/dev/AI/supervisor/bin/supervisor-bridge",
-      "env": {
-        "SUPERVISOR_URL": "http://localhost:3200/mcp"
-      }
+      "type": "http",
+      "url": "http://koala:30320/mcp"
     }
   }
 }
 ```
 
-Build the bridge binary once: `task bridge:build`
+The supervisor MCP server is reachable over Tailscale at `koala:30320` (NodePort
+to the in-cluster service on port 3200). No local binary or stdio shim is
+required — Claude Code talks to it directly via HTTP.
 
-Then open Claude Code in your project — run `/mcp` to confirm `supervisor` is listed.
+Open Claude Code in your project — run `/mcp` to confirm `supervisor` is listed.
 
 ## A typical TDD session