[danielporterda]

Stack position

3 of 7. Depends on #1257; next: #1259.

What changed

• Compiles validated authored MDX into ordinary Mintlify MDX.
• Selects prose and snippet branches together, and fetches only the selected branch.
• Removes all custom <IfVersion> / <Snippet> syntax before Mintlify sees the page.
• Emits snippets as inert fenced code with a fence longer than any source backtick run.
• Adds resolved-commit provenance and deterministic sibling *.source.mdx → *.mdx output/drift helpers.

No production page opts in in this PR, so existing served content remains unchanged.

Validation

• python3 -m pytest tests/test_inline_snippet_compiler.py tests/test_inline_snippet_source.py tests/test_inline_snippet_parser.py
• Ruff, DCO, and git diff --check

Review focus

Please focus on branch-selection correctness, non-selected-content exclusion, MDX injection resistance, and generated-file ownership.