fix(plugin-docs-cli): mask inline code before HTML checks

[sunker]

What this PR does / why we need it:

Angle-bracket placeholder text inside inline code (e.g. <slug> in a URL example) was being flagged as a raw HTML tag, since the no-raw-html check only skipped fenced code blocks, not inline backtick spans. This PR adds a maskInlineCode() helper that neutralizes inline code spans before the HTML-tag regex runs.

Also adds a new unfilled-section-brief validation rule that fails strict validation if a page still contains a scaffolded <!-- section-brief:start --> marker, so an unfilled documentation stub can never ship silently.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Both issues were found while manually testing the panel-docs codemod (#2834) against a real plugin.

[Copilot]

Pull request overview

This PR improves @grafana/plugin-docs-cli validation correctness and content completeness checks by preventing inline-code placeholders (e.g., <slug>) from being misinterpreted as raw HTML, and by adding a rule to catch unfilled scaffolded documentation stubs before publishing.

Changes:

• Add maskInlineCode() and apply it to the raw-HTML tag detector so inline backtick spans don’t trigger false positives.
• Introduce a new strict-mode validation rule (unfilled-section-brief) to fail (or warn in non-strict mode) when scaffold markers remain in docs pages.
• Add unit tests covering inline-code masking behavior and stub-marker detection.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/plugin-docs-cli/src/validation/types.ts	Adds the new unfilled-section-brief rule identifier to the shared rule registry.
packages/plugin-docs-cli/src/validation/rules/utils.ts	Introduces maskInlineCode() helper for neutralizing inline code span contents on a line.
packages/plugin-docs-cli/src/validation/rules/utils.test.ts	Adds unit tests validating maskInlineCode() behavior across common inline-code patterns.
packages/plugin-docs-cli/src/validation/rules/stub-content.ts	Adds a new rule runner to detect leftover section-brief:start scaffold markers in markdown pages.
packages/plugin-docs-cli/src/validation/rules/stub-content.test.ts	Adds coverage for stub-content detection, strict vs non-strict severity, line numbers, and multi-file behavior.
packages/plugin-docs-cli/src/validation/rules/markdown.ts	Updates matching logic to optionally mask inline code before running specific regex checks (used for raw HTML).
packages/plugin-docs-cli/src/validation/rules/markdown.test.ts	Adds regression tests ensuring inline-code placeholders don’t trigger no-raw-html, while real HTML still does.
packages/plugin-docs-cli/src/validation/rules/index.ts	Registers the new checkStubContent rule in the rule runner pipeline.

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[mckn]

LGTM! Left two nits/questions

[mckn]

Is it any value in running these lines in the getCodeBlockLines or maskInlineCode? I'm asking since the other rules seems to use those functions to check for code.

[mckn]

Do we also need to verify that there is an end block? Or will this fail if it is missing?