feat(mcp): adopt mainstream server-qualified MCP tool naming

Research across 8 multi-server agent clients (Claude Code, Codex, Gemini
CLI, VS Code, Cline, Roo Code, Goose, OpenCode) showed all of them keep
the server namespace in model-facing MCP tool names; the RFC's premise
for raw names ("servers already prefix their tools") is false for the
official GitHub/filesystem/Sentry servers.

- Config: drop toolPrefix; require serverName ([A-Za-z0-9_-]{1,32}),
  duplicate serverName fails the later instance at load (per-root
  reservation, released on dispose)
- Names: always mcp__<serverName>__<rawName>; normalize to the DeepSeek
  64-char [A-Za-z0-9_-] contract with a deterministic 12-hex identity
  hash on lossy normalization; raw name is the only thing sent on the
  wire (tools/call)
- Sync: two-phase fetch/swap — fetch failure keeps the previous
  generation; a swap conflict rolls back the whole generation (never a
  partial set); duplicate raw names reject the tool list
- RFC: moved to implemented/ (status + skeleton rewritten per the
  format contract), naming design + tier-level test coverage recorded
- Tests: naming algorithm unit suite; keyless Streamable HTTP e2e
  against an in-process StreamableHTTPServerTransport (namespace
  discovery, execution, per-request auth headers); dotted-name
  normalization e2e via a new fixture tool

packages/mcp/mcp-client/tests/fixture-server.ts

@@ -51,5 +51,15 @@ server.registerTool('image', {
   ],
 }))
 
+// Dotted name: legal in MCP, illegal in the DeepSeek function-name contract.
+// Exercises the bridge's normalize-and-hash public-name path end to end.
+server.registerTool('admin.reset', {
+  title: 'Admin Reset Tool',
+  description: 'Tool with a dotted name (normalization test).',
+  inputSchema: {},
+}, async () => ({
+  content: [{ type: 'text', text: 'reset done' }],
+}))
+
 const transport = new StdioServerTransport()
 await server.connect(transport)