[flexdinesh]

• Behavior owner and resulting change: useFileNavigation owns one visible file set; new hideReviewed state (sessionStorage, per stream) removes reviewed files from it, so the file tree, diff list, Alt+J/K and collapse-all all follow. A "Hide reviewed files" icon toggle sits beside the file filter.
  • Marking the in-view file reviewed hides it at once; selection and scroll move to its next visible neighbor, so long files don't strand scroll position.
  • Empty results show "All files reviewed" (tree and diff) with a "Show reviewed files" action; text filter composes ("All matching files reviewed").
  • Comment navigation to a hidden reviewed file turns hiding off, mirroring how it clears the text filter.
• Contracts/invariants affected; local/remote implications: frontend only; no API or storage change. Same behavior in both modes.
• Validation results; remaining risks: mise run check passes (92 browser tests incl. new "hide reviewed files filters the tree and diff together"). Verified manually in light/dark, desktop and 390px drawer, keyboard focus ring. Risk: comment-navigation-to-hidden-file path is untested by browser tests.
• Intentional architecture/design changes and rationale: DESIGN.md, development.md and user docs record the toggle, ownership and persistence.
• UI evidence: toggle matches the 28px filter field and --border-muted; pressed uses the shared accent toggle state. No Pierre geometry change.