[mcp] Add escalations_get tool with pagination defaults

[rahul-roy-glean]

Description

Adds a new escalations_get MCP tool with built-in pagination (limit/offset) and a default limit of 50 to prevent unbounded response sizes.

Related Issue

Slack report: escalations_get is called with empty params {}, returning a 21MB response body. This PR adds the tool with safe defaults so empty params return a bounded result set.

Motivation and Context

The escalations_get tool existed on the remote Glean MCP server but was missing from the local MCP server. When called with {}, the remote version returns every escalation (~21MB). This change:

1. Adds the tool to the local MCP server
2. Enforces a default limit=50 (max 100), so empty {} calls return a bounded result
3. Adds offset for pagination, allowing callers to page through results when needed
4. Keeps the tool surface minimal — all params are optional with sensible defaults

This is the "smallest safe change" approach: default limit first, explicit pagination via offset as an escape hatch.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Code refactoring
• Build/CI pipeline changes
• Other (please describe):

How Has This Been Tested?

• Unit tests
• Integration tests
• Manual testing
• Other (please describe):

Tests added:

• src/test/tools/escalations.test.ts — 15 tests covering schema validation (JSON schema snapshot, empty params, query, limit/offset, rejection of invalid values), API integration (default pagination, query filtering, offset pagination), and response formatting (empty results, null, normal results, pagination hints, description truncation)
• server.test.ts — 3 integration tests for end-to-end tool execution via callToolHandler (default pagination, query filter, pagination with hasMoreResults)
• MSW mock handler in mcp-test-utils for POST /rest/api/v1/escalations

Checklist

• My code follows the code style of this project
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have checked for potential breaking changes and addressed them

Additional Notes

No existing flows are broken — escalations_get is a net-new tool in the local MCP server. The remote MCP server's equivalent tool is unaffected since this change only touches the local server.

Files changed:

• packages/local-mcp-server/src/tools/escalations.ts — New tool implementation (schema, API call via raw fetch, response formatter)
• packages/local-mcp-server/src/server.ts — Register tool in TOOL_NAMES, listToolsHandler, and callToolHandler
• packages/mcp-test-utils/src/mocks/handlers.ts — MSW mock for the escalations endpoint
• packages/local-mcp-server/src/test/tools/escalations.test.ts — Unit tests
• packages/local-mcp-server/src/test/server.test.ts — Integration tests

Slack Thread