Step 5/12 of docs/superpowers/plans/2026-05-17-files-overlay-rewrite.md.
Adds a server-rendered editor page for creating a new file in a target
folder. Renders the same overlay_file_editor.html as the edit route,
but with is_new=True so the template:
* Hides the Delete button
* Hides the Download link (no file to download yet)
* Changes the Save button label to "Create"
* Emits data-at-folder on the textarea for the JS save handler to
compose path = at_folder + "/" + filename
* Updates the title block (browser tab + heading) to "New file" /
"<at_folder>/…new file"
The existing edit route now passes is_new=False and at_folder=""
explicitly so both call sites are explicit about the contract.
Path validation: ?at may be empty (overlay root) or a relative folder
path. safe_resolve_for_listing rejects traversal attempts (400). A
missing or non-directory at returns 404. Reused the helper to keep
the safety story identical to the listing / edit routes.
Phase B Step 5 is server-side only — no JS changes here. Step 6
migrates openEditorTextNew in editor.js to use this route via
window.modals.openRouted().
Tests added (tests/test_url_addressable_modals.py):
* test_new_route_renders_with_empty_content
* test_new_route_renders_with_target_folder_attribute
* test_new_route_renders_create_button_not_save
* test_new_route_400s_for_invalid_at_path
* test_new_route_404s_for_non_files_overlay
pytest: 573 → 578 passed, 1 skipped, 3 deselected.
Verified live: curl /overlays/2/files/new returns markup with
data-at-folder="", "UTF-8 · 0 bytes" byte count, save button label
"Create", and no Delete / Download buttons.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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