docs: renumber the README layer table so it matches the "3 layers" claim

[rajarshidattapy]

Description

README.md:31 says:

On top of live browser control, WebCMD adds 3 layers of learnings.

The table directly beneath it numbered four rows, 1. through 4., starting with Live browser control — the thing the sentence says the layers sit on top of. So the README claimed three layers and then showed four.

This renumbers the table 0.–3., which makes the prose literally true: layer 0 is live browser control, and layers 1–3 are the three learnings built on it. No prose changes were needed.

Closes #204

Note on the "collapses cost" sentence

The same paragraph ends with "Each layer collapses cost and variance for the layer above it." I checked whether that direction was also wrong and it is correct — reading down the table, each row makes the row above it cheaper: a sitemap makes live browsing cheaper, an authored adapter makes sitemap-guided work cheaper, and a tailored command makes adapter authoring cheaper. Left untouched.

Type of Change

• 🐛 Bug fix
• ✨ New feature
• 🌐 New site adapter
• 📝 Documentation
• ♻️ Refactor
• 🔧 CI / build / tooling

Checklist

• I ran the checks relevant to this PR
• I updated tests or docs if needed
• I included output or screenshots when useful

Notes on the checklist:

• Docs-only change to four table rows in README.md. No code, tests, or generated artifacts are touched.
• The change is confined to the hand-written section above ## Demo; the generated community-plugins table between the webcmd-community-plugins markers is untouched, so npm run check-community-plugins is unaffected.

Adapter Notes

Not applicable — no adapter is added or modified in this PR.

• Updated generated or lean docs when command discoverability changed
• Used positional args for the command's primary subject unless a named flag is clearly better
• Normalized expected adapter failures to CliError subclasses instead of raw Error

Screenshots / Output

One file, +4 / -4:

 | Layer | Scenario | What Webcmd Helps With |
 | --- | --- | --- |
-| 1. Live browser control | The site is unfamiliar. | … |
-| 2. Sitemap memory | … | … |
-| 3. CLI authoring | … | … |
-| 4. Extend existing CLIs | … | … |
+| 0. Live browser control | The site is unfamiliar. | … |
+| 1. Sitemap memory | … | … |
+| 2. CLI authoring | … | … |
+| 3. Extend existing CLIs | … | … |

Rendered, the table now reads as one base layer plus the three learnings the sentence promises.

[github-actions]

🟢 No documentation gap found — medium confidence

The automated review found no documentation gap in the supplied changes.

This review is advisory and does not block merging.