feat(page): DocsUI::Endpoint + FieldTable/ErrorTable — the endpoint-reference kit

[mhenrixon]

Closes #14. Part of #8 (Phase 2).

Problem

The gem had zero API-documentation vocabulary. Every API page in a consuming site repeated the same shape by hand — an HTTP-method badge + path, a parameters table, and an error table — with per-page row helpers (err_row, field_row, scope_row, event_row) redefined across files with drifting arities and inconsistent "no value" placeholders ("-" vs "—").

What this adds

Three thin, composable pieces plus a Section extension. Documenting an endpoint's reference material is now declarative and renders identically across every site.

1. DocsUI::Endpoint.new(method, path)

A method badge + monospace path, rendered inline so it drops straight into a Section description or a run of prose.

• Verb → colour is a frozen Hash of literal class strings so the Tailwind scan (which reads the gem's Ruby) generates every badge class: GET → badge-success, POST → badge-primary, PATCH/PUT → badge-warning, DELETE → badge-error.
• An unknown verb falls back to a neutral badge and never raises — a typo degrades gracefully.
• Accepts a Symbol or String; the label is upcased.

2. Section#description accepts a Phlex component

DocsUI::Section("Create a message", description: DocsUI::Endpoint.new(:post, "/v1/messages"))

A component instance is matched before the callable branch (a Phlex component also responds to #call, so order matters). The existing String and proc forms are untouched — covered by unchanged passing specs.

3. DocsUI::FieldTable + DocsUI::ErrorTable

Keyword-schema presets over Table:

• FieldTable.new(fields) — each { name:, type:, required: false, description: } → Name (code-styled) / Type / Required (✓ or the canonical em-dash —) / Description.
• ErrorTable.new(errors) — each { scenario:, status:, type:, param: nil } → Scenario / Status / Type (code) / Param (code). The Param column is auto-hidden when no row names a param.

Descriptions honour Table's cell convention, so [:md, "…"] renders inline Markdown today.

Test plan

Spec	Validates
endpoint_spec.rb	badge class per verb; path monospace; upcasing; unknown verb → neutral (no raise); inline rendering; HTML escaping
field_table_spec.rb	name code-styled; required tick vs canonical em-dash; [:md, …] description; composition over Table; escaping
error_table_spec.rb	type code-styled; Param column present iff any row has a param (asserts the <td> count); composition; escaping
section_spec.rb	a Phlex component instance description renders in place; existing String/proc specs untouched

Verification

• bundle exec rspec — 187 examples, 0 failures (92% line coverage)
• bundle exec rubocop — no offenses
• cd docs && bun run build:css — badge-success / badge-primary / badge-warning / badge-error / badge-neutral all present in the compiled CSS, proving the scan caught the literal frozen-Hash classes
• Backwards compatible — the existing Section description forms are covered by untouched passing specs

Dogfood

The components reference page (docs/) gains an "Endpoint, FieldTable & ErrorTable" section rendering a realistic POST /api/webhook_endpoints example live, and the README component table lists all three.

Out of scope (per the issue)

• Request/response example components (next issue).
• OpenAPI ingestion into these components (possible follow-up epic).
• Migrating app-4's pages (consumer follow-up; these components are their landing spot).