fix(mcp): forward RBAC role and move tool injection to base agent

[mrveiss]

Summary

• RBAC forwarding (Bug: MCP dispatch fallback doesn't forward user role for RBAC filtering #2629): _try_mcp_dispatch() and _dispatch_tool_call() now accept and forward role parameter to dispatcher.dispatch()
• Base agent injection (Enhancement: Extend MCP tool injection to all agent types, not just ChatAgent #2631): Moved _get_mcp_tools_prompt() from ChatAgent to StandardizedAgent base class — all agents now inherit MCP tool injection
• Cache fallback (Enhancement: Extend MCP tool injection to all agent types, not just ChatAgent #2631): _ensure_cache_fresh() wrapped in try/except — stale cache used on registry timeout instead of blocking
• Extract method: _build_unknown_tool_error() extracted from _dispatch_tool_call() for function length compliance

Closes #2629
Closes #2631

Test plan

• 18/18 tests passing (15 dispatch + 3 chat agent)
• All existing tests pass with base class method inheritance
• Patch paths updated for base class location

[github-actions]

⚠️ SSOT Configuration Compliance: Violations Found

Metric	Count
Total Violations	2
SSOT Violations (high priority)	1
Other Violations	1

⚠️ 1 values have SSOT config equivalents!

These should be replaced with SSOT config imports:

Python:

from src.config.ssot_config import config
# Use: config.vm.main, config.port.backend, config.backend_url

TypeScript:

import config from '@/config/ssot-config'
// Use: config.vm.main, config.port.backend, config.backendUrl

📖 See SSOT_CONFIG_GUIDE.md for documentation.