fix(platform): share folder-name validation in create and rename

[yannickmonney]

What changed

• Share the existing canonical folder-name constraints between the backend, Create and Rename: trimmed NFC name, 128-character limit, no separators/control characters, and no single/double-dot names.
• Create now explains invalid names inline before submission. A structured FOLDER_NAME_INVALID refusal also maps to the name field without clearing or disabling the draft; corrected retries succeed.
• Reuse documents.folder.invalidName and folder.nameRequired, already translated in EN/DE/FR with de-CH fallback. No new or untranslated strings.
• Add boundary, valid-control, canonicalization and editable-retry regressions; document automated coverage.

Verification

• RED on origin/main: 7 new Create dialog regressions fail; 7 existing/valid controls pass.
• GREEN: 29 dialog tests and 365 scoped server/shared-rule/consumer/guard tests pass across 19 files (one worker).
• Scoped TypeScript check passes (changed files and their imported dependencies; 1800 MiB heap).
• Type-aware oxlint: 7 files, zero diagnostics; scoped oxfmt and diff checks pass. Knowledge manual-guide reference check passes.
• Real Chromium: 10 cases pass across Create/Rename and EN/DE/FR/de-CH, including input retained after server refusal and corrected retry. Uses actual dialogs/design system with synthetic mutation transport, not a live authenticated backend.
• Final visual-aspect-analyzer gate: baseline, Create and Rename each score 100 with zero defects and nonempty detected elements. Screenshots and reports retained in the task delivery box.

Whole-platform tests, whole-workspace types and production checks are left to CI/authorized operators. Independent review requested separately; no self-acceptance or merge.

Closes #3629

Current-main rebase

Replayed the previously accepted source b8cdf1cbb6c7492534d01e33ff95ef5810ef3b2b onto main d1373d84cd56972501403f62145ec52e6f65d44a, including the merged shared CI repair in #4625. The accepted feature payload and all current-main changes are preserved in one atomic commit. Configured commit and conflict checks pass; earlier behavioral proof remains recorded above. All seven native required checks and full merge-group validation remain required for this new source.

Maintenance replay: preserves the accepted feature payload on current main 7d178ca. Includes the merged #4649 Knip cleanup and the exact independently accepted one-line shared CLI inventory repair from #4654 (252f0df), which is still pending native merge on main. The fixed suite inventory keeps its discovery and source/compiled phase guards. Existing feature proof is retained; no fresh full-feature/full-workspace test or hosted-green claim. Native required checks remain mandatory.

[yannickmonney]

Independent review: accept at exact head 2da4cc47dc0a6419dccd14f79f59eb9c6ff41027.

Evidence reviewed:

• folderNameSchema is the single client rule used by Create and Rename; backend validateFolderName consumes the same shared reason/max/separator/control/dot logic.
• Create and Rename map FOLDER_NAME_INVALID to the name field without reset/close/toast, and the tests assert the invalid value remains editable and a corrected retry succeeds.
• Tests cover both separators, 128/129 boundaries, dot names, DEL/control coverage, canonicalization, and valid names; EN/DE/FR contain documents.folder.invalidName, with the existing documented de-CH overlay fallback to DE.
• On origin/main, Create still only trims/nonempty-validates before submitting, so the Bug: Create folder hides invalid-name rules that Rename already explains #3629 regression is present in the base.

Unrun: the targeted jsdom suite could not reach assertions in this checkout because Vite loaded zod with z.string/z.number undefined (16 pre-assertion failures). No CI checks were rerun or waited on. Formal approval was unavailable because the authenticated reviewer is the PR author account; this comment is the accept record.