Document Pathfinder and community feedback across the contributor docs

Moves the README's deep material into .readme/ (walkthrough, autonomous
loop, status line, metrics, test bot) and brings AGENTS.md, the .agents-docs
set and QUICK-REFERENCE.md in line with Step 0 and the metrics ingestion
flow.

AI Assisted

.readme/autonomous-loop.md

@@ -0,0 +1,64 @@
+# Autonomous Loop
+
+`plan2code-loop` is a CLI that works through your spec's tasks on its own, one agent call at a
+time. It is an **alternative to Step 3**, not a replacement — the four-step workflow and the specs it
+produces are unchanged.
+
+← [Back to README](../README.md)
+
+---
+
+## When to use it instead of Step 3
+
+| Approach | Best for |
+|----------|----------|
+| `/plan2code-3-implement` | Interactive control, reviewing each phase, logic that needs your judgment |
+| `plan2code-loop` | Straightforward implementations, batch work, overnight runs |
+
+The loop reads the same `overview.md` and phase files. You can start with the loop and finish by
+hand, or the reverse — the checkboxes are the only handoff.
+
+---
+
+## Install
+
+```bash
+# From the plan2code root directory
+node install.js     # A  (everything + dev tools)  — or  C → O  (loop only)
+```
+
+## Run
+
+```bash
+plan2code-loop    # fully interactive
+```
+
+It will:
+
+1. Find specs in `./specs/`
+2. Let you pick one if there are several
+3. Offer to resume an existing session
+4. Ask for a JIRA ticket ID, which agent to drive, the loop mode, and a max iteration count
+
+Then, per iteration: read `overview.md` and the phase files, find the first unchecked task (or
+phase), implement it, mark the checkbox, repeat — until everything is done or it hits the iteration
+cap.
+
+---
+
+## Loop modes
+
+| Mode | Each agent call | Git commits | Best for |
+|------|-----------------|-------------|----------|
+| **One task per loop** (default) | Implements a single task | The Node controller commits after each task | Smaller models, cautious execution |
+| **One phase per loop** | Implements every task in a phase | The agent commits after each task, with the JIRA ID | Larger context windows, tightly related tasks |
+
+Session state lives per-spec in `specs/<feature>/.plan2code-loop/`, so each feature's progress
+stays isolated.
+
+---
+
+## Full documentation
+
+Architecture, completion markers, agent adapters, and configuration:
+[`plan2code-loop/README.md`](../plan2code-loop/README.md)