chore: remove image, vision, TTS, and MoA tools from codebase

[avoidwork]

Description

Removes four non-core tools from the agent tool registry: image_generate, vision_analyze, text_to_speech, and mixture_of_agents. This simplifies the codebase, reduces attack surface, and eliminates unnecessary API key requirements (FAL_API_KEY, OPENAI_API_KEY, OPENROUTER_API_KEY) for tools outside the core agent workflow.

Type of Change

• Bugfix (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
• Refactor (no functional change)
• Performance improvement
• CI / build / tooling

Testing

• All 763 tests pass with 0 failures
• Deleted 5 test files along with the tools they tested
• Updated tests/unit/tool_index.test.js to remove orphaned env-var mocks
• npm run coverage passes; coverage.txt updated by pre-commit hook

Coverage

• 100% line coverage maintained

Checklist

• npm run lint passes (oxlint + oxfmt via pre-commit hook)
• Tests pass with 100% line coverage
• No forbidden patterns used
• Conventional Commit style applied

Files Changed

Action	File
Deleted	src/tools/image.js
Deleted	src/tools/vision.js
Deleted	src/tools/tts.js
Deleted	src/tools/moa.js
Deleted	tests/unit/tools_image.test.js
Deleted	tests/unit/tools_vision.test.js
Deleted	tests/unit/tools_tts.test.js
Deleted	tests/unit/tools_moa.test.js
Deleted	tests/unit/tool_registration.test.js
Modified	src/tools/index.js (removed imports, permissions, factories, switch cases)
Modified	docs/FLOWS.md (removed tool references)
Modified	tests/unit/tool_index.test.js (removed orphaned env-var mocks)
Modified	coverage.txt
Added	OpenSpec change artifacts (proposal, design, specs, tasks)