Cut the README to a way in and let the docs carry the depth

[TheGreatAxios]

Closes CL-7884.

Summary

251 lines to 131. A first-time reader had to get past three permission subsections, a stack table, an architecture diagram, and the full director catalog before reaching anything that told them whether to keep going.

What was deleted, not moved

Architecture, the stack list, extensibility, and the agent-workspace catalog are deleted. Each is already covered in docs/, verified before removing rather than assumed:

Removed from README	Confirmed covered in
Architecture + reactor diagram	docs/ARCHITECTURE.md
Permission rule enumeration	docs/ARCHITECTURE.md, docs/PRODUCT.md
Stack table	docs/IMPLEMENTATION.md
Extensibility	docs/PLUGINS.md, docs/MCP.md, docs/HOOKS.md
Director catalog, .agents/agents/, search_agents	docs/ARCHITECTURE.md, docs/PRODUCT.md, docs/IMPLEMENTATION.md

Moving them would have bolted a "from the README" paragraph onto docs that already explain the thing better. Two copies of an explanation is one copy that goes stale, and it is never the docs copy.

What replaced the permission section

~50 lines of enumerated rules became a paragraph: auto mode runs ordinary work without prompting, stops for dependency installs / recursive deletes / paths outside the workspace / anything credential-shaped, and refuses shell-based file editing outright. Then a pointer to the full policy.

This is the judgement call worth reviewing. Auto mode is the feature most likely to surprise a new user, and a paragraph may be too little. I flagged it as uncertain on the issue rather than pretending otherwise.

Structure

What it is → install → first run → permissions → where to go next → contributing → license. The docs/ table moves from the footer to a signposted next step, and AGENTS.md gets a line saying what it is for.

Testing

Docs only. bun run lint and tsc --noEmit clean via the pre-commit gate. Links checked by inspection; the quickstart commands are unchanged from the current README, so they are as correct as they were before — I did not re-run them from a clean clone, which the issue asks for and remains unticked.

[linear-code]

CL-7884

[TheGreatAxios]

Audit: Approve (CL-7884, 0.3.25)

Fit summary: README trim 251→131 lines. Deletions verified covered in docs/code; permission paragraph accurate. No scope creep beyond the trim.

Non-blocking nit (follow-up, not a merge blocker — intentionally not edited here): the Contributing paragraph adds an ungrounded 'will be declined' enforcement claim. Suggest softening to a guidance statement or grounding it in CONTRIBUTING.md in a follow-up PR.