Persistent output: notify user once instead of console-spamming when the block can't be located

[nelsonlove]

Summary

With Persistent Output enabled, running a run-<lang> block (or any block whose editor range can't be resolved, e.g. live preview) logs Error finding output target: Probably because of 'run-' prefix to the console on every chunk of stdout, while the user gets no visible indication that their output isn't being saved to the note.

This PR:

• Shows a single Notice per run explaining what happened: "persistent output isn't supported for this code block ('run-' blocks and live preview) — the output is only shown below the block, not saved to the note."
• Stops the per-chunk console.error spam, and removes the setViewData(editor.getValue()) call in that error path (it rewrote the identical document on every output chunk)
• Downgrades the constructor-time range-lookup failure to a clearer console.warn

On-screen output behavior is unchanged.

Testing

• npm run build passes (tsc + esbuild)
• Manually verified: with persistent output on, a run-lisp block now shows the Notice once and produces no per-chunk console errors; the happy path (block range resolved) is untouched by this change

🤖 Generated with Claude Code

[nelsonlove]

Superseded by #449, which includes these commits and rewrites the persistent output path they patch. Closing to reduce reviewer noise — if the smaller change is preferred over the rewrite, this can be reopened.