Extract mcp-server to its own repo (meshtastic/meshtastic-mcp) (#10861)

The Python MCP server + hardware test harness that lived under mcp-server/
now has its own home at https://github.com/meshtastic/meshtastic-mcp
(published, versioned independently). Remove the in-tree copy and wire the
firmware repo to the standalone server externally.

- Delete mcp-server/ (96 files) and the 8 harness-coupled AI workflow files
  under .claude/commands/ and .github/prompts/ that drove ./mcp-server/
  run-tests.sh — those workflows now ship with meshtastic-mcp as skills.
- .mcp.json: register the server via
  `uvx --from git+https://github.com/meshtastic/meshtastic-mcp meshtastic-mcp`
  instead of a local ./mcp-server/.venv, keeping MESHTASTIC_FIRMWARE_ROOT="."
  so the MCP tools still work from this checkout with no local build.
- Repoint the remaining references (AGENTS.md, CLAUDE.md,
  .github/copilot-instructions.md, bin/regen-*.sh, docs, Screen.h,
  userPrefs.jsonc, test/fixtures/nodedb/README.md, .trunk/configs/.bandit)
  at the standalone repo. The MCP tool surface is unchanged — only the
  pytest harness moves out; run it from a meshtastic-mcp checkout with
  MESHTASTIC_FIRMWARE_ROOT pointed here.

No build/CI/platformio coupling existed, so nothing in the firmware build
changes.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

test/fixtures/nodedb/README.md

@@ -20,7 +20,7 @@ geography.
    build/fixtures/nodedb/nodes_v25_<N>.proto  ← .gitignored, fresh timestamps
               ↓
    - Portduino: cp to ~/.portduino/<config>/prefs/nodes.proto
-   - Hardware: XModem upload via mcp-server's push_fake_nodedb tool
+   - Hardware: XModem upload via the meshtastic-mcp push_fake_nodedb tool
 ```
 
 ## What's committed
@@ -121,10 +121,11 @@ cp build/fixtures/nodedb/nodes_v25_1000.proto ~/.portduino/default/prefs/nodes.p
 # Run the native binary; loadFromDisk picks it up at boot.
 ```
 
-### Push to USB-attached hardware via mcp-server
+### Push to USB-attached hardware via meshtastic-mcp
 
 ```python
-# From within the mcp-server tool surface:
+# From within the meshtastic-mcp tool surface
+# (https://github.com/meshtastic/meshtastic-mcp):
 push_fake_nodedb(
     size=500,
     target="hardware",