Optimize standard library documentation analysis

[julia-script]

Summary

• build standard-library documentation from one multi-root ProjectAnalysis
• migrate doctest, documentation-site, policy, generation, and inventory consumers
• add a structural regression test proving shared modules are analyzed once while preserving private filtering
• fail fast when the shipped manifest and embedded source map disagree

Performance

Gate	Before	After
documentation policy	19.68s	2.43s
documentation check	19.91s	2.37s
documentation examples	39.74s	22.30s

This removes approximately 52 seconds from the compiler package test command. Policy still checks all 45 modules and all 54 doctests pass.

Verification

• pnpm typecheck
• pnpm test — 28/28 package tasks passed
• pnpm release:candidate — 9/9 tests passed
• Biome passes on every file in this PR
• compiler documentation policy, check, examples, and inventory all pass

The aggregate pnpm check was also attempted locally, but its initial Biome step stopped on trailing whitespace in an unrelated uncommitted BootstrapEvaluation.ts edit that is not included in this PR.