feat: scaffold knowledge base as shared skill with symlinked reference

[l50]

Key Changes:

• Knowledge base documents are now created as fleet-level skills (skills/<name>-guide/SKILL.md) instead of inline reference files, enabling cross-host portability via Skill("name") loading
• Agent scaffolding creates a relative symlink from references/<name>-guide.md to the skill file, preserving squad's agent.yaml injection while supporting on-demand loading in Claude Code
• System prompt template updated to load the knowledge base via Skill() instead of hardcoded Read paths, eliminating machine-specific absolute path breakage
• Documentation and tests updated to reflect the new fleet layout and symlink-based reference strategy

Added:

• writeReferenceSkill function in scaffold/scaffold.go that creates the skill directory at <agentsDir>/skills/<name>-guide/SKILL.md, renders the reference template into it, then creates a relative symlink from <agent>/references/<name>-guide.md back to the skill file
• YAML frontmatter block to reference.md.tmpl with name and description fields, making the rendered document a valid named skill loadable by the Skill tool
• Skill added to the default tools: list in system.md.tmpl so agents can invoke Skill("name") out of the box
• Test coverage in scaffold_test.go for the happy-path fleet layout (skill exists, symlink resolves, content matches) and four error branches: skills dir blocked by a file, SKILL.md path occupied by a directory, stale reference link that cannot be removed, and read-only references directory blocking symlink creation

Changed:

• Agent scaffolding in scaffold.go replaced the direct references/<name>-guide.md file entry in the files map with a call to writeReferenceSkill, and updated the post-creation log message to point users to skills/<name>-guide/SKILL.md
• Knowledge base loading instruction in system.md.tmpl changed from Read with a relative path to Skill("{{.Name}}-guide"), removing any dependency on filesystem path resolution
• README.md.tmpl file table updated to reference ../skills/<name>-guide/SKILL.md as the canonical location, with a note that references/<name>-guide.md symlinks to it for squad injection
• Documentation in creating-agents.md updated to describe the skill-plus-symlink layout, replace the absolute-path fallback phrasing with Skill("criteria"), and explicitly warn against hardcoding absolute paths in agent bodies

[codecov]

Codecov Report

❌ Patch coverage is 92.85714% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
scaffold/scaffold.go	92.85%	1 Missing and 1 partial ⚠️

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