pi bridge: RemoteMcpClient is now the only copy (pi-extensions retired mcp-loader.ts)

pi-extensions 750b2a8 removed mcp-loader.ts in favour of pi's built-in MCP
support (builtin:mcp, ~/.pi/agent/mcp.json). The bridge's RemoteMcpClient was
vendored from that file and kept in step by an MCP-STREAMABLE-HTTP-CLIENT-SYNC
token, checked by scripts/check-mcp-client-sync.sh. With the canonical copy
gone the guard could only ever SKIP (or, on images that still bake
/opt/pi-extensions/extensions/mcp-loader.ts, compare against a dead file), so
it is removed rather than left looking like a check.

Comment and README only; no code change. The bridge still type-strips and
imports (node 24), and evaluateDormancy is exported as before. The README
records why MemPalace itself does not move to the built-in: its wake-up,
mailbox, feed and stamping need their own client, and built-in tools would be
mcp__mempalace__* with codemode exposure by default.

extensions/pi/README.md

@@ -211,12 +211,16 @@ chosen at load time:
   also pins `Host`/`Origin`, so a request arriving under the wrong hostname is
   refused even when the port is open.
 
-  Implementation note: the HTTP client (`RemoteMcpClient`) is **vendored** from
+  Implementation note: the HTTP client (`RemoteMcpClient`) was **vendored** from
   [`pi-extensions`](https://gitea.jordbo.se/joakimp/pi-extensions)'
-  `mcp-loader.ts`. A `MCP-STREAMABLE-HTTP-CLIENT-SYNC` token keeps the two
-  copies from drifting — [`scripts/check-mcp-client-sync.sh`](../../scripts/check-mcp-client-sync.sh)
-  fails if they diverge (it skips gracefully when the `pi-extensions` checkout
-  isn't present).
+  `mcp-loader.ts`. That loader was retired on 2026-10-12 (pi-extensions
+  `750b2a8`) in favour of pi's built-in MCP support, so this copy is now the
+  only one. The sync token and `scripts/check-mcp-client-sync.sh` that guarded
+  the pair were removed with it. MemPalace itself does **not** move to the
+  built-in: the bridge's wake-up, mailbox, feed and provenance stamping need
+  their own client, and built-in MCP tools would be renamed
+  `mcp__mempalace__*` with `codemode` exposure (not declared to the model) by
+  default.
 
 ## Fail-soft
 

extensions/pi/mempalace.ts

@@ -576,17 +576,15 @@ class StdioMcpClient implements IMcpClient {
 // ───────────────────────────────────────────────────────────────────────
 // RemoteMcpClient — EXTERNAL transport (streamable-HTTP / sessionless JSON-RPC).
 //
-// VENDORED from pi-extensions/extensions/mcp-loader.ts (class RemoteMcpClient).
-// Kept as a copy rather than a shared import because the two repos ship
-// independently; the canonical implementation lives in mcp-loader.ts. Port
-// protocol fixes in both directions.
+// ORIGIN: vendored from pi-extensions/extensions/mcp-loader.ts (class
+// RemoteMcpClient). mcp-loader.ts was RETIRED on 2026-10-12 (pi-extensions
+// 750b2a8) in favour of pi's built-in MCP support, so THIS copy is now the only
+// one. There is no canonical partner left to sync with, so the former
+// MCP-STREAMABLE-HTTP-CLIENT-SYNC token and scripts/check-mcp-client-sync.sh
+// were removed with it. The last canonical version is
+// `git show a88fa99:extensions/mcp-loader.ts` in pi-extensions.
 //
-// MCP-STREAMABLE-HTTP-CLIENT-SYNC: v1
-// This token must match the canonical block's. Bump it in BOTH files whenever
-// the streamable-HTTP protocol handling changes; scripts/check-mcp-client-sync.sh
-// fails when they diverge (skips gracefully if pi-extensions isn't checked out).
-//
-// Deltas from the canonical copy:
+// Deltas from that last canonical copy:
 //   • protocolVersion pinned to "2024-11-05" to match mempalace-mcp's stdio
 //     handshake (the server echoes whatever it is sent, so cosmetic today,
 //     but keeps both transports consistent).