fix(spec)!: examples are delimited (heading / --- / prose); remove the Gherkin compat layer

[aslakhellesoy]

Fixes #61.

1. Examples are delimited (ADR 0012)

The only documented way to write a multi-table example was the "hug" — a step
paragraph directly beneath a table with no blank line. That is not valid GFM: the
step parses as another table row, so the layout does not render on GitHub and does
not survive prettier/markdownlint (the formatter silently rewrites the spec,
sometimes into a passing example that asserts nothing).

New rule: an example runs from one delimiter to the next. There are three
delimiters:

• a heading (#…######),
• a thematic break (---), and
• a paragraph that matches no step (prose).

Consecutive matching paragraphs (with their attached tables/doc strings) merge
into one shared-state example, so a multi-table flow is ordinary, formatter-stable
GFM:

Given the following users have been imported:

| email | name |
| ----- | ---- |
| a@b.c | Ada  |

And the following assets have been imported:

| name  |
| ----- |
| Moose |

Ported to all seven ports (TypeScript, Python, Ruby, Rust, .NET, Go, Java/Kotlin).
Drift now uses span overlap, which also closes a blind spot: deleting a step
def from the middle of a merged example turns that paragraph into prose, splitting
the example so the now-dead paragraph is reported as drift. New conformance bundle
18-multi-table-example locks the merge, the prose delimiter, and state isolation
across every port.

2. The Gherkin compatibility layer is removed

The delimiter model made multi-scenario .feature files merge (scenarios are
separated only by a blank line). Rather than grow the compat layer to compensate,
we removed it entirely as feature creep:

• the gherkinTables / gherkinDocStrings / gherkinKeywords scanner plugins,
• the @varar/cucumber package,
• the generic scannerPlugins config field + JSON-schema property + the
  ScannerPlugin / scan(plugins) extension mechanism (gherkin was its only
  user), across all seven ports and every wiring point (vitest plugin/runtime,
  CLI, runner, LSP, language index, website worker).

Migration: Varar no longer runs .feature files. Hand your .feature files to
a coding agent and ask it to translate them into Markdown specs and Varar step
definitions — the rewritten Varar for Cucumber users
page maps every Gherkin-ism, including Scenario Outline → header-bound table.

Breaking changes

• Two step-only examples separated by only a blank line now run as one
  shared-state example — separate them with a --- or a heading. Prose between the
  steps of one example ends it.
• Varar no longer runs Gherkin .feature files; the scannerPlugins config key is
  removed and is now an unknown-key error.

Docs

• Rewrote the examples reference ("Where an example begins and ends", naming, the
  attachment/hug section).
• Deleted the "Run your existing .feature files" how-to; rewrote "Varar for
  Cucumber users" into a Gherkin→Varar mapping; cleaned up configuration.md and
  markup-is-yours.md.

Verification

make check green across all seven ports + commit-lint. Full TS gate (typecheck,
lint, tests, knip, jscpd) and the website build pass. Branch coverage held at the
gate by adding a failure-anchor unit test rather than lowering the threshold.

🤖 Generated with Claude Code

https://claude.ai/code/session_01SqKahEdcXvVEYXt2zuYQwJ