Ignore literal <embed-code> examples inside Markdown fenced blocks

[Copilot]

The parser treated literal <embed-code> snippets in documentation examples as real embedding instructions, which caused check-mode failures and panics in docs that demonstrate usage. This change makes fenced Markdown examples non-actionable while keeping real embedding behavior unchanged.

• Parser behavior: distinguish docs examples from real embed instructions

  • Track normal Markdown fence state (marker + indentation) while scanning regular lines.
  • Skip <embed-code...> recognition when currently inside a non-embedding Markdown fenced block.

• Fence handling: make closing detection marker-aware

  • Store the opening fence marker for active embedding code blocks.
  • Close only on a valid matching fence (same marker kind, sufficient marker length, no trailing content), preventing premature closure on lines like ```kotlin.

• Regression coverage

  • Added a fixture with a fenced Markdown sample that contains a literal <embed-code> block and inner code fences.
  • Added an embedding test asserting this doc is processed without embedding parse errors and remains up-to-date.

````markdown
<embed-code
  file="$root/version.gradle.kts"
  start="val validationVersion"
  end="val validationVersion">
</embed-code>
```kotlin
val validationVersion by extra("2.0.0-SNAPSHOT.419")

```

[alexander-yevsyukov]

@armiol, @Oleg-Melnik, FYI.

[chatgpt-codex-connector]

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[dmytro-kashcheiev]

@alexander-yevsyukov LGTM from my side.

[alexander-yevsyukov]

@copilot please act on the comments.

[Copilot]

@copilot please act on the comments.

Addressed in 40ac5f8 (plus cleanup in b479d80). I applied the requested backticks-only fence parsing fix and added regression coverage.

[alexander-yevsyukov]

LGTM

[Vladyslav-Kuksiuk]

LGTM