Fix Windows file locking error when rendering with --output-dir

[cderv]

When rendering with --output-dir on Windows without a project file, Quarto would fail with:

ERROR: os error 32: remove 'path\.quarto'

Root Cause

When --output-dir is used without a project file, Quarto creates a "synthetic" project context with a temporary .quarto directory to manage the render. The issue was a timing problem in cleanup ordering:

1. Rendering completes
2. Code tries to remove .quarto directory
3. But the Deno KV database file inside .quarto is still open
4. context.cleanup() (which closes the KV file) is called later by the caller
5. Windows doesn't allow deleting open files → error 32

Fix

Call context.cleanup() before attempting to remove the .quarto directory. This ensures file handles are properly closed first.

The fix is minimal (5 lines) and safe because cleanup() is idempotent (wrapped with once()), so calling it early and again later has no side effects.

Alternative Approach Considered

Initially implemented a path registration mechanism where code could register paths for cleanup at the point of decision. This added cleanupPaths array and registerForCleanup() method to ProjectContext, with cleanup logic duplicated across 4 locations.

This was deemed too complex for a single use case (82 lines across 6 files). The simpler ordering fix achieves the same result.

Documentation

Added comments explaining the "synthetic project" pattern:

• When --output-dir is used without _quarto.yml, Quarto creates a temporary project context
• The forceClean flag signals this is temporary and needs cleanup
• Creation: src/command/render/render-shared.ts:52-58
• Cleanup: src/command/render/project.ts:889-907

Added tests in tests/smoke/render/render-output-dir.test.ts covering both default cleanup behavior and --no-clean flag preservation.

Fixes #13625

This should also probably be backported as this is common problem, and could explain quarto preview lock issue in positron (which I think use --output-dir for some files)

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