Previously, generateInstructions() iterated over AvailableToolsets() which
returns all toolsets that have tools defined, rather than only the enabled
toolsets based on WithToolsets() configuration.

This caused instructions for all toolsets to be included regardless of which
toolsets were actually enabled, leading to bloated instructions (e.g., 5886
chars vs 1226 chars when only 'repos' toolset is enabled).

Changes:
- Add EnabledToolsets() method to return only enabled toolset metadata
- Update generateInstructions() to use EnabledToolsets()
- Add regression test for the fix

Fixes #1897

Updates to v2.2.0 which includes server instructions diff support for
detecting issues like #1897.

Add toolsets-context and toolsets-issues,context configurations to
improve test coverage for instruction generation with different
toolset combinations.

Bumps [SamMorrowDrums/mcp-server-diff](https://github.com/sammorrowdrums/mcp-server-diff) from 2.2.0 to 2.3.5.
- [Release notes](https://github.com/sammorrowdrums/mcp-server-diff/releases)
- [Commits](SamMorrowDrums/mcp-server-diff@v2.2.0...v2.3.5)

---
updated-dependencies:
- dependency-name: SamMorrowDrums/mcp-server-diff
  dependency-version: 2.3.5
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Bumps golang from 1.25.4-alpine to 1.25.6-alpine.

---
updated-dependencies:
- dependency-name: golang
  dependency-version: 1.25.6-alpine
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

- Extract storeLine() and accumulate() helper closures to eliminate
  duplicated line processing and truncation logic
- Simplify main loop by using early return pattern (newlineIdx < 0 -> break)
- Add test for empty response body edge case
- Add test for exact maxLineSize boundary condition (10MB)

The refactored code reduces nesting and makes the flow clearer:
accumulate handles byte collection with truncation detection,
storeLine handles ring buffer storage with truncation markers.