Why: the user asked for a reviewable plan covering (a) previews for
office/image/markdown/code files and web links, docked in the right rail
or the system overlay, (b) keeping artifact deletion as a capability with
no UI entry, and (c) implementing fs tools without enabling them.
Evidence: the proposal assesses each idea against current architecture,
defines the FilePreview capability component with a format matrix and
lazy-loaded office parsers, the SSRF-guarded url-preview endpoint, the
gated sandboxed fs tool family, four delivery phases with acceptance
criteria, and decision points D1-D5 for the user.
Impact: documentation only; implementation follows in a separate task
after D1-D5 are settled.
Refs: task feature/file-preview-proposal; extends 2026-09-30
ui-redesign-and-auth.md section 9.
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