docs: inventory and route Scient documentation

[yaacovcorcos]

Summary

• add a generated exhaustive Markdown inventory for exact clean candidate revisions of Scient, scient-desktop, and the website
• explicitly exclude scient-agent without inspecting its inherited OpenCode Markdown
• add a compact cross-product capability map that routes to nearest implementation, Help, architecture, and roadmap owners
• add a temporary reviewed disposition ledger covering all document collections and named exceptions
• preserve inherited paths and defer broad movement until three maintenance pilots prove a better structure

Evidence

• 1,204 tracked Markdown files: Scient 124, desktop 1,074, website 6
• 928 desktop vendored donor files structurally excluded
• 33 desktop Help pages retained as canonical authored sources
• zero paths left in the generator's unreviewed role
• generator tests, JSON integrity/count/uniqueness checks, local Markdown links, formatting, and git diff --check pass

Dependency

Depends on #103. Desktop and website candidate revisions are recorded exactly in the generated artifact; this PR does not merge or rewrite those repositories.

Documentation impact: Updated — docs/product/scient-capability-map.md, docs/planning/documentation-disposition-ledger-2026-08-28.md, docs/research/documentation-inventory-2026-08-28.generated.json, indexes, and generator/tests.

[yaacovcorcos]

Superseded by merged #107, which consolidates this inventory foundation on current Scient main and pins the final generated inventory to the merged Desktop and Website documentation heads. This PR remains available as implementation history.