docs: restructure into docs/<skill-family>/, slim README to install + overview

[potiuk]

Summary

Reshape the top-level README into the framework's adoption entry point — overview + 3-family table + 3-step bootstrap + submodule-update reminder, in 113 lines (was 1110). All detailed content moves into a new docs/ tree split by skill family so adopters can read only the family they care about.

New layout

/
├── README.md (slim — 113 lines)
├── AGENTS.md, CONTRIBUTING.md, NOTICE, LICENSE  (unchanged at root)
└── docs/
    ├── prerequisites.md            (general prereqs — Claude Code,
    │                                Gmail MCP, GitHub auth, etc.)
    ├── setup/
    │   ├── README.md               (family overview + link map)
    │   ├── secure-agent-setup.md   (moved from root)
    │   └── secure-agent-internals.md (moved from root)
    ├── security/
    │   ├── README.md               (family overview + link map)
    │   ├── process.md              (16-step lifecycle + Mermaid +
    │   │                            label lifecycle — extracted)
    │   ├── roles.md                (Who-this-guide-is-for + Shared
    │   │                            conventions + per-role workflow
    │   │                            guides — extracted)
    │   ├── how-to-fix-a-security-issue.md  (moved from root)
    │   └── new-members-onboarding.md       (moved from root)
    └── pr-management/
        └── README.md               (family overview + adopter contract)

What stays in the README

• Project overview (1 paragraph)
• Skill-family table (setup / security / pr-management)
• 3-step adopter bootstrap (git submodule add + cp -r _template/ + ln -s .claude/skills/)
• Keeping the submodule current (post-merge hook)
• Cross-reference pointers

What moved out

Content	New location
Process reference (16 steps + Mermaid)	docs/security/process.md
Label lifecycle	docs/security/process.md
Role guides (For triager / dev / RM)	docs/security/roles.md
Who-this-guide-is-for + Shared conventions	docs/security/roles.md
Prerequisites for running framework skills	docs/prerequisites.md
secure-agent-setup.md	docs/setup/
secure-agent-internals.md	docs/setup/
how-to-fix-a-security-issue.md	docs/security/
new-members-onboarding.md	docs/security/

Cross-references

Updated everywhere — links from non-moved files to the moved ones now use the new path; links inside the moved files to root-level files (README.md, AGENTS.md, .claude/skills/, tools/, projects/) gain the ../../ prefix. doctoc TOCs regenerated for every changed .md.

Test plan

• All pre-commit hooks pass (markdownlint, typos, doctoc, check-placeholders)
• All step anchors in process.md are reachable from roles.md (the (#step-N) refs in roles.md were rewritten to (process.md#step-N))
• No bare references to the four moved root docs remain anywhere outside docs/<family>/
• Reviewer eyeballs the README to confirm it reads as the adopter entry point
• Reviewer browses each docs/<family>/README.md for accuracy
• CI link-check (lychee) passes

🤖 Generated with Claude Code