Acknowledge .tldraw files from tldraw offline

[frolic]

People are saving files out of tldraw offline and trying to open them elsewhere. Those are .tldraw files — archives holding a zipped SQLite database and its assets, rather than the JSON a .tldr file holds — so nothing in this plugin can read one. Until support lands, this recognizes the extension and explains that.

Before this, a .tldraw file in the vault landed on Obsidian's generic "no view for this file type" screen, with nothing to say tldraw was involved.

This only detects the extension — it does no parsing.

The message links to tldraw offline itself and to the export instructions in its user manual, so it points somewhere rather than just saying no. Both are built as nodes by a shared helper: Obsidian's Notice only renders a link when given a fragment rather than a string, and the file view needs the same copy.

The new view extends FileView directly rather than BaseTldrawFileView, which reads the file as text and parses it as JSON; on an archive that just produces an opaque Unable to parse TldrawFile. The view type is deliberately kept out of VIEW_TYPES, since including it would let updateViewMode fall through to setMarkdownView and flip a binary file into the markdown editor.

Claiming the extension takes away Obsidian's own handling for unrecognized files, so the view offers "open in default app" — otherwise opening a .tldraw in the vault would leave the user with no route to a program that can actually read it.

Two things worth flagging in the diff:

• importTldrawFile now returns undefined instead of throwing when there's nothing to import. None of its three callers had a try/catch, so throwing would have surfaced as an unhandled rejection with no user feedback.
• The extension check is case-insensitive. File dialogs on macOS and Windows match their filters that way, so Drawing.TLDRAW is selectable and would otherwise have slipped through to the JSON parser.

Not covered: ![[drawing.tldraw]] embeds inside a note still fall through to Obsidian's default handling, since embedRegistry only registers tldr.

Test plan

1. Save a file from tldraw offline so you have a .tldraw file, and put it in a vault.
2. Click it in the file explorer — expect "Can't open .tldraw files yet" rather than Obsidian's unknown-file screen.
3. Use the "Open in default app" action in the tab bar, and the same item in the tab context menu.
4. Run "Import file as new document and open in a new tab" and pick the .tldraw file — expect a notice, and no unhandled error in the console.
5. Rename it to .TLDRAW and repeat step 4 — same notice.
6. Confirm .tldr files still open, import, and embed exactly as before.