MCP: remove superseded Python facade and mesh

[fredporter]

Outcome

• removes the bespoke /api/mcp REST facade, handler registry, guardrails, and mutating self-heal
• removes the hard-coded peer/GitHub mesh and duplicate Snackbar MCP routes
• removes stale launchers, manifests, diagnostics, maintenance code, and implementation-only tests
• removes the misleading MCP daemon panel and false HTTP-service probes
• stops startup from validating or auto-starting the retired stack
• aligns current Developer help, workspace setup, Plates spec, and architecture evidence
• preserves the canonical official-SDK udos-mcp stdio gateway unchanged

Contraction

• 4,817 lines removed; 53 lines added
• 54 files changed

Verification

• 412 remaining backend tests passed
• 12 frontend tests passed
• frontend production build passed
• 3 canonical udos-mcp protocol tests passed
• changed-file Ruff, docs, governance, route audit, and diff checks passed
• zero live /api/mcp or retired-module references remain