feat(line): add ridgeline as a Line variant (#143)

* feat(line): add ridgeline as a Line variant

One distribution per series, stacked at a fixed pitch on a single shared
amplitude. Ships three static examples (light, dark, full editorial),
the type-line.md spec, and a geometric gate.

verify-ridgeline.py derives the figure's one amplitude and its baseline
pitch from the figure itself, then holds every vertex to both. It also
checks the drawn baseline rules, the shared bin scale, absolute M/L/Z
only, the overlap ceiling, the focus pairing and every label binding.
test-verify-ridgeline.py proves each check in both polarities and pins
the scope treaty with the sibling Line gates.

The contract binds data-bins on a <path>, which no other chart in the
repo declares, so verify-slopegraph and this gate never claim the same
file.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(verify-ridgeline): read exponent coordinates as numbers, not commands

parse_d scanned for [A-Za-z] independently of the numbers, so the `e` in a
valid scientific-notation coordinate such as 4.4e2 was counted as a path
command. The explicit-command rule then rejected a correct ridgeline with a
message about command counts.

Tokenise the d attribute left to right with the number branch tried first,
so an exponent is consumed as part of its number. A letter that survives
that branch is a real command and still faces the M/L/Z vocabulary check;
anything else leaves the path unreadable, which stays a finding.

Adds both polarities: a shipped coordinate rewritten as 4.4e2 must verify,
and a falsified one written the same way must not.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: 0xDarkMatter <0xDarkMatter@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -249,6 +249,16 @@ jobs:
         id: sankey_tests
         run: python scripts/test-verify-sankey.py
 
+      - name: Verify ridgeline shared amplitude
+        if: always()
+        id: ridgeline
+        run: python scripts/verify-ridgeline.py --all
+
+      - name: Verify ridgeline checker
+        if: always()
+        id: ridgeline_tests
+        run: python scripts/test-verify-ridgeline.py
+
       # lint-render.py's oracle is pixels, so the browser is part of the contract:
       # pin Playwright exactly, and let that pin choose the Chromium build. Bump
       # both together, deliberately, by editing PLAYWRIGHT_VERSION.
@@ -325,6 +335,8 @@ jobs:
           echo "| Slopegraph Checker | ${{ steps.slopegraph_tests.outcome == 'success' && '✅ Passed' || (steps.slopegraph_tests.outcome == 'skipped' && '⏭️ Skipped' || '❌ Failed') }} |" >> $GITHUB_STEP_SUMMARY
           echo "| Sankey Flow Conservation | ${{ steps.sankey.outcome == 'success' && '✅ Passed' || (steps.sankey.outcome == 'skipped' && '⏭️ Skipped' || '❌ Failed') }} |" >> $GITHUB_STEP_SUMMARY
           echo "| Sankey Checker | ${{ steps.sankey_tests.outcome == 'success' && '✅ Passed' || (steps.sankey_tests.outcome == 'skipped' && '⏭️ Skipped' || '❌ Failed') }} |" >> $GITHUB_STEP_SUMMARY
+          echo "| Ridgeline Shared Amplitude | ${{ steps.ridgeline.outcome == 'success' && '✅ Passed' || (steps.ridgeline.outcome == 'skipped' && '⏭️ Skipped' || '❌ Failed') }} |" >> $GITHUB_STEP_SUMMARY
+          echo "| Ridgeline Checker | ${{ steps.ridgeline_tests.outcome == 'success' && '✅ Passed' || (steps.ridgeline_tests.outcome == 'skipped' && '⏭️ Skipped' || '❌ Failed') }} |" >> $GITHUB_STEP_SUMMARY
           echo "| Primitive Icons & Documentation | ${{ steps.icons.outcome == 'success' && '✅ Passed' || (steps.icons.outcome == 'skipped' && '⏭️ Skipped' || '❌ Failed') }} |" >> $GITHUB_STEP_SUMMARY
           echo "| Render Linter Self-Test | ${{ steps.render_selftest.outcome == 'success' && '✅ Passed' || (steps.render_selftest.outcome == 'skipped' && '⏭️ Skipped' || '❌ Failed') }} |" >> $GITHUB_STEP_SUMMARY
           echo "| Rendered Layout (paint oracle) | ${{ steps.render.outcome == 'success' && '✅ Passed' || (steps.render.outcome == 'skipped' && '⏭️ Skipped' || '❌ Failed') }} |" >> $GITHUB_STEP_SUMMARY