docs: add README, CLAUDE.md, and anonymised profiles.txt for public release

CLAUDE.md

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+# Instagram Scraper — Agent Context
+
+## What this project is
+
+A Playwright-based Instagram scraper. Reads `profiles.txt`, visits each profile in a real Chromium browser, scrapes the last N posts, and writes `output.csv` + `output.md`.
+
+## How to run
+
+```bash
+uv run python scraper.py        # run the scraper
+uv run pytest tests/ -v         # run unit tests
+uv run playwright install chromium  # install browser (first time only)
+```
+
+Always use `uv run` — never `python` directly or `pip`.
+
+## Key files
+
+| File | Purpose |
+|---|---|
+| `scraper.py` | All logic: auth, profile scraping, post scraping, output |
+| `profiles.txt` | Input: one Instagram URL per line |
+| `auth_state.json` | Saved Playwright session (gitignored, created on first run) |
+| `output.csv` | Scraped results (gitignored) |
+| `output.md` | Scraped results in Markdown (gitignored) |
+| `tests/test_parsers.py` | Unit tests for pure parsing functions |
+
+## Architecture
+
+Single script, no framework. Key functions in `scraper.py`:
+
+- `extract_hashtags(text)` / `extract_mentions(text)` — pure regex, fully tested
+- `profile_slug_from_url(url)` — extracts username from URL
+- `read_profiles()` — reads `profiles.txt`, strips line number prefixes
+- `is_logged_in(page)` / `ensure_authenticated(browser)` — session management
+- `get_post_urls(page, profile_url)` — collects post links from profile grid
+- `scrape_post(page, post_url, profile_slug)` — extracts all fields from a post
+- `write_csv(posts)` / `write_markdown(posts)` — output writers
+- `main()` — orchestrates everything
+
+## Output fields
+
+`profile`, `post_url`, `date` (ISO 8601), `caption`, `likes`, `image_urls` (comma-separated CDN URLs), `hashtags`, `mentions`, `location`, `media_type` (photo/video/carousel)
+
+## DOM selectors (verified against live Instagram)
+
+Instagram uses atomic CSS — class names change. These structural selectors are stable:
+
+- **Post grid links**: `a[href*="/p/"]`
+- **Date**: `time[datetime]` → `.get_attribute('datetime')` (first element = post date)
+- **Caption**: JS tree walker over text nodes in `section` containing a link to the profile slug; filter `len > 20`, skip relative times
+- **Likes**: First `span` with purely numeric text
+- **Images**: JS `img[src*="cdninstagram"]` filtered by `width > 100` and excluding `/s150x150/`
+- **Carousel**: `button[aria-label="Next"]` exists
+- **Video**: `video` element exists
+- **Location**: `a[href*="/explore/locations/"]` — filter out text "Locations" (footer link)
+
+## Auth flow
+
+1. Check for `auth_state.json` → load with `browser.new_context(storage_state=...)`
+2. If missing or expired → open visible browser, wait for user to log in manually, save with `context.storage_state(path="auth_state.json")`
+
+## Modifying behaviour
+
+- Change number of posts: edit `POSTS_PER_PROFILE` constant at top of `scraper.py`
+- Change input/output paths: edit `PROFILES_FILE`, `OUTPUT_CSV`, `OUTPUT_MD` constants
+- To re-authenticate: delete `auth_state.json` and re-run
+
+## Testing policy
+
+Pure functions (`extract_hashtags`, `extract_mentions`, `profile_slug_from_url`, `read_profiles`) have unit tests. Browser functions are tested end-to-end only — do not mock the browser.
+
+## Dependencies
+
+- `playwright>=1.40.0` — browser automation
+- `pytest>=7.0.0` (dev) — test runner
+- Standard library only: `re`, `csv`, `sys`, `pathlib`, `itertools`