Add e2e showcase tests

[Vladyslav-Kuksiuk]

This PR adds showcase end-to-end tests.

Resolves this issue.

[MykytaPimonovTD]

Not sure, but think that path from root will be better, and in name the name will be enough.

[single-source.yml](/showcase/configuration/single-source.yml)

[Vladyslav-Kuksiuk]

Root paths didn't work, when clicking the link.

[Copilot]

Pull request overview

Adds a runnable “showcase” that doubles as end-to-end validation for embed-code-go by embedding curated fixtures into documentation examples (positive and negative), and wiring a dedicated test suite to execute the full check → embed → check flow.

Changes:

• Introduces an opt-in (-tags showcase) Ginkgo/Gomega E2E test suite that runs embed-code-go via go run against temporary copies of the showcase docs.
• Adds a new showcase/ documentation + fixture tree covering embedding features, configuration shapes, and intentional failure scenarios.
• Links the showcase from top-level docs and runs the showcase suite in CI.

Reviewed changes

Copilot reviewed 50 out of 50 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
showcase/showcase_test.go	E2E Ginkgo suite running check/embed flows
showcase/README.md	Entry README for showcase + how to run
showcase/embedding/README.md	Index of embedding feature examples
showcase/embedding/positive/whole-file-source.md	Positive example: whole-file embedding
showcase/embedding/positive/start-end-pattern.md	Positive example: start/end patterns
showcase/embedding/positive/source-line-pattern.md	Positive example: line pattern
showcase/embedding/positive/pattern-escaping.md	Positive example: escaping glob syntax
showcase/embedding/positive/overlapping-fragments.md	Positive example: overlapping fragments
showcase/embedding/positive/named-source-root.md	Positive example: named source roots
showcase/embedding/positive/named-fragment.md	Positive example: named fragments
showcase/embedding/positive/multi-part-fragment-separator.md	Positive example: multi-part fragments + separator
showcase/embedding/positive/multi-line-pattern.md	Positive example: multi-line patterns (\n)
showcase/embedding/positive/markdown-fence-shielding.md	Positive example: inert instructions inside fences
showcase/embedding/positive/instruction-tag.md	Positive example: paired vs self-closing tags
showcase/embedding/positive/html-showcase.html	Positive example: HTML document processing
showcase/embedding/positive/comment-filtering.md	Positive example: comment filtering modes
showcase/embedding/negative/stale.yml	Negative config: stale snippet scenario
showcase/embedding/negative/processing-errors.yml	Negative config: processing error scenarios
showcase/embedding/negative/docs/unclosed-code-fence.md	Negative doc: unclosed fence
showcase/embedding/negative/docs/stale-snippet.md	Negative doc: intentionally stale snippet
showcase/embedding/negative/docs/missing-source.md	Negative doc: missing source file
showcase/embedding/negative/docs/missing-pattern.md	Negative doc: unmatched line pattern
showcase/embedding/negative/docs/missing-fragment.md	Negative doc: missing fragment
showcase/embedding/negative/docs/missing-code-fence.md	Negative doc: missing code fence
showcase/embedding/negative/docs/invalid-attributes.md	Negative doc: invalid attribute combination
showcase/embedding/embed-code.yml	Config for running positive embedding showcase
showcase/configuration/single-source.yml	Config example: single (unnamed) source root
showcase/configuration/README.md	Guide for YAML configuration patterns
showcase/configuration/named-sources.yml	Config example: named source roots
showcase/configuration/multiple-embeddings.yml	Config example: multiple embedding entries
showcase/configuration/include-exclude.yml	Config example: includes/excludes
showcase/configuration/docs/single-source/greeting.md	Docs for single-source config
showcase/configuration/docs/named-sources/text-line.md	Docs for named text source
showcase/configuration/docs/named-sources/kotlin-greeting.md	Docs for named Kotlin source
showcase/configuration/docs/named-sources/java-greeting.md	Docs for named Java source
showcase/configuration/docs/multiple/kotlin/greeting.md	Docs for multi-embedding Kotlin entry
showcase/configuration/docs/multiple/java/greeting.md	Docs for multi-embedding Java entry
showcase/configuration/docs/include-exclude/included.md	Docs for included file behavior
showcase/configuration/docs/include-exclude/excluded.md	Docs for excluded file behavior
showcase/code/text/glob-patterns.txt	Text fixture for pattern examples
showcase/code/kotlin/org/showcase/KotlinGreeting.kt	Kotlin fixture with fragment markers
showcase/code/java/org/showcase/PatternSamples.java	Java fixture for pattern/range examples
showcase/code/java/org/showcase/OverlappingFragments.java	Java fixture for overlapping fragments
showcase/code/java/org/showcase/MultiPartWorkflow.java	Java fixture for multi-part fragments
showcase/code/java/org/showcase/Greeting.java	Java fixture used across many examples
showcase/code/java/org/showcase/CommentModes.java	Java fixture for comment filtering
README.md	Links to showcase + minor doc fix
go.mod	Updates copyright header year
EMBEDDING.md	Links to showcase + minor doc/link formatting
.github/workflows/check.yml	Runs showcase tests in CI with build tag

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[Oleg-Melnik]

LGTM, with Copilot comments resolved before merging.