feat(core): render change-scoped context extracted-first

Context:
========
`CompileContext` mixed pre-change metadata with post-delta content,
warned spuriously for new specs and cache misses, and applied lock
optimizations that described stale content.

Changes:
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- Render scoped specs from the merged preview set in all modes
- Type optimization warnings as `missing-optimization` / `stale-optimization`
- Stop relaying regeneration as a warning in the shared sink
- Traverse manifest deps before repository access; skip ghosts silently