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/status-line.md

@@ -0,0 +1,54 @@
+# Claude Code Status Line
+
+A persistent three-line status bar for Claude Code: model, project, git branch, uncommitted diff
+stats, session duration and cost, context-window usage, and plan quota.
+
+It reads everything from the JSON Claude Code already sends on stdin — **no API calls, no auth, no
+background processes.** Optional, and unrelated to the workflow itself.
+
+← [Back to README](../README.md)
+
+---
+
+## What it looks like
+
+On Pro / Max / Teams accounts, where rate limits are available:
+
+```
+◦ ◦  Opus 5 / high │ plan2code │ feature/PCWEB-11702-pathfinder │ +12 -3
+╭●╮  ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄
+├■┤  3h 5m ($4.62) │ ▰▰▰▰▰▱▱▱▱▱▱▱ 42% (84K) │ 5h: 28% · 7d: 61%
+```
+
+On Enterprise / Bedrock / Vertex / pay-as-you-go, where they aren't, the last segment becomes session
+token counts instead:
+
+```
+◦ ◦  Sonnet 5 │ plan2code │ main │ +12 -3
+╭●╮  ┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄
+├■┤  2m ($0.18) │ ▰▰▱▱▱▱▱▱▱▱▱▱ 18% │ 88k in · 3k out
+```
+
+The icons down the left are Planny, the project mascot.
+
+---
+
+## Install
+
+```bash
+node install.js     # A  (everything + dev tools)  — or  C → S  (status line only)
+```
+
+That copies the script to `~/.claude/plan2code-statusline.js`, writes a default config to
+`~/.claude/statusline-config.json` (an existing config is preserved), and registers it in
+`~/.claude/settings.json`.
+
+If you already have a custom `statusLine` entry, the installer asks before replacing it and backs the
+old one up. Uninstalling removes the script and the settings entry but leaves your config file alone.
+
+---
+
+## Full documentation
+
+Config options, compact mode, thresholds, and troubleshooting:
+[`src/statusline-claude/README.md`](../src/statusline-claude/README.md)