feat: installer-first get-started funnel plus dev.to crosspost and weekly metrics scripts

[abrichr]

Summary

Growth-launch "ops-docs" lane for docs.openadapt.ai.

1. Get-started funnel rewrite (docs/get-started/index.md, docs/get-started/first-workflow.md)

• Primary install path is now the uv installer pair:

  curl -LsSf https://astral.sh/uv/install.sh | sh
  curl -fsSL https://raw.githubusercontent.com/OpenAdaptAI/openadapt-flow/main/scripts/install.sh | sh

• The pip two-command path (pip install 'openadapt[browser]' → openadapt quickstart) sits directly below, labeled "Manual path". Shell-specific quoting tabs are kept on first-workflow under the manual label.
• Page links early to the hosted demo, template gallery, and blog.
• Plain definition added at the first use of the word: "Qualification means we test your workflow against real failures before it runs."
• Filenames unchanged, so mkdocs.yml nav is untouched. docs/llms.txt (hand-maintained surface; no generator found in-repo) updated to track the new get-started descriptions.

2. scripts/crosspost_devto.py — reads the blog RSS (verified from blog Hugo config: https://blog.openadapt.ai/index.xml; /feed.xml is not served) and creates dev.to articles via POST /api/articles with canonical_url set to the original post URL. Dry-run ON by default; idempotent by checking existing canonical URLs via GET /api/articles/me/all; API key only from DEVTO_API_KEY; stdlib + httpx only.

3. scripts/metrics_weekly.py — writes deterministic reports/growth-metrics-YYYY-WW.md: GitHub stars/forks (OpenAdapt, openadapt-flow, openadapt-capture), HN Algolia hits with summed points/comments, pypistats 7-day downloads (openadapt, openadapt-flow), blog post count from sitemap. reports/ gitignored. Documented in new scripts/README.md with a suggested weekly cron line; no cron workflow shipped.

4. llms.txt — updated per existing hand-maintenance pattern (item 4 above).

Dependency flag (needs sequencing)

The prescribed raw.githubusercontent install URL 404s until OpenAdaptAI/openadapt-flow PR #387 (growth/installer-first branch adds scripts/install.sh) lands on main. This PR should merge after that one, or the docs quickstart breaks. Not merged here.

Verification

• uv run pytest tests/ -q → 238 passed (15 new: fixture-feed dry-run offline-safe, idempotency planning, pagination, apply-path with mocked HTTP; metrics report rendering determinism + mocked-HTTP collection, zero network in tests)
• uv run mkdocs build --strict → passes
• uv run python scripts/validate_docs.py → Validation passed! (product-doc contract intact)
• python scripts/crosspost_devto.py --dry-run-equivalent against tests/fixtures/sample_feed.xml runs fully offline
• metrics_weekly.py --help works; live read-only run produced a correct W34 table
• ruff check on all changed Python files → clean

Notes / minor deviations

• Added httpx>=0.27 to the dev extra (task specifies stdlib+httpx); uv.lock diff is otherwise format-only metadata churn (lock revision 3 upload-time fields) — no package versions changed.
• Removed first-workflow's pointer to the older https://openadapt.ai/install.sh one-liner since it competes with the canonical two-command path (the hosted script itself remains served for the landing page).