feat(docs): add workflow to publish s2-docs markdown to orphan branch

[GarthDB]

Add GitHub Actions workflow to publish docs/s2-docs markdown files to a docs-markdown orphan branch for chatbot indexing.

This is Phase 1 of publishing markdown content - Phase 2 will add markdown-generator output alongside s2-docs content in PR #696.

Changes

• Added .github/workflows/publish-markdown.yml workflow
• Workflow triggers on pushes to docs/s2-docs/**, after successful Release workflows, and on manual dispatch
• Publishes only *.md files from docs/s2-docs/ to the docs-markdown orphan branch under s2-docs/

Orphan Branch Layout

After this PR merges, the docs-markdown branch will contain:

docs-markdown (orphan branch)
└── s2-docs/
    ├── INDEX.md
    ├── README.md
    ├── components/
    ├── designing/
    ├── developing/
    ├── fundamentals/
    └── support/

Phase 2 (in PR #696) will add components/, tokens/, and registry/ directories alongside s2-docs/.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 804caab

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[GarthDB]

Run report for 804caabc

Total time: 6.9ms | Comparison time: 0s | Estimated loss: 6.9ms (100.0% slower)

	Action	Time	Status	Info
🟩	SyncWorkspace	6.8ms	Passed

Touched files

.github/workflows/publish-markdown.yml