refactor: merge skill tool into slashcommand to reduce system prompt size

[Luodian]

Summary

Merges the separate skill tool into the existing slashcommand tool, eliminating duplicate skill list descriptions that waste ~2,400+ tokens per session.

Fixes #1666

Problem

The skill list was duplicated across multiple tool descriptions:

Location	Content
skill tool description	Full <available_skills> XML with every skill name + description
slashcommand tool description	Full <available_skills> with every skill + command
Sisyphus system prompt	Skill table with name + description for each skill

With ~80 installed skills at ~30 tokens each, this wastes ~4,800+ tokens on pure duplication.

Solution

1. Removed skill tool registration - slashcommand already handles both skills and commands
2. Enhanced slashcommand with MCP capability formatting (previously only in skill tool)
3. Removed skill table from Sisyphus prompt - replaced with reference to slashcommand tool
4. Updated all references from skill tool to slashcommand tool in prompts

Changes

• src/index.ts - Removed skill tool creation and registration, pass MCP options to slashcommand
• src/tools/index.ts - Removed createSkillTool export
• src/tools/slashcommand/tools.ts - Added extractSkillBody(), formatMcpCapabilities(), MCP support in formatLoadedCommand()
• src/tools/slashcommand/types.ts - Added mcpManager and getSessionID options
• src/tools/skill-mcp/tools.ts - Updated hint to reference slashcommand tool
• src/agents/sisyphus.ts - Updated tool references from skill to slashcommand
• src/agents/sisyphus-prompt-builder.ts - Removed duplicate skill table, updated references

Token Savings

• Skill list in tool descriptions: 1 copy instead of 2 (~2,400 tokens saved)
• Skill table in Sisyphus prompt: removed (~2,400 tokens saved)
• Total: ~4,800+ tokens saved per session for users with many skills

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Summary by cubic

Merged the skill tool into slashcommand to eliminate duplicate skill lists and cut ~4.8k tokens per session. Slashcommand now shows skill details (incl. MCP capabilities) and preserves git-master config defaults.

• Refactors

  • Removed the skill tool; prompts/agents now reference slashcommand for skills.
  • Slashcommand returns skill output when the name matches a skill: extracts the skill body, shows the base directory, lists MCP tools/resources/prompts; injects git-master config with defaults preserved.
  • Added and wired options: mcpManager, getSessionID, and gitMasterConfig; updated tool registry and types; updated skill_mcp hint.

• Migration

  • Update any custom prompts or workflows that call the "skill" tool to use "slashcommand".

^{Written for commit 41b454c. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 7 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Requires human review: Large refactor merging skill tool into slashcommand tool (118 lines added). Changes MCP integration, tool routing, and core agent prompts. Cannot be 100% sure of no regressions without testing skill加载}