🛡️ Sentinel: [HIGH] Fix path traversal in URL interpolation

[davidruzicka]

This PR addresses a critical security vulnerability reported by Sentinel:

Vulnerability: Path Traversal in Composite Tool Execution
Impact: CompositeExecutor substituted user-provided arguments directly into API path templates without escaping dots. Input like ../admin could resolve to GET /admin, allowing access to unintended API endpoints.
Fix: Modified encodePathSegment in src/mcp/mcp-server.ts and resolvePath in src/tooling/composite-executor.ts to replace dot characters (.) with %2E after standard encodeURIComponent.
Verification: Added src/tooling/composite-executor-security.test.ts to ensure path traversal attempts are safely encoded to %2E%2E and executed the full test suite (npm run test), which passed.

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PR created automatically by Jules for task 4876818639075587945 started by @davidruzicka

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

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