fix: Figma picker rate limits and board-link errors

[lexdoudkin]

The live Figma account hit two errors: the picker traversed every library page and exhausted the gateway rate budget, and sending a question with an empty board link exposed Failed to construct 'URL': Invalid URL.

Load one page of Minds and Audiences on connection, then offer explicit Load more and canonical Mind search through shared UI controls. Blank or malformed board links automatically open setup with a specific instruction before any export, upload or Study creation. Connection progress now distinguishes browser approval from loading the library.

Validation: full npm run check passed; Chromium exercised both Mind and Audience selection plus empty-board-link recovery; 27 bridge tests passed. Added large-account pagination, selection-preserving search, encoded search routing and malformed-link checks. Live transport requests were independently verified from an opaque browser iframe after deployment of PR #54.

Refs minds-ai-co/webapp#7998. The earlier gateway/edge mismatch is deployed at main e3bb4523beaa4fbe13791e53d30fa70218731908; this follow-up fixes the newly observed live-account issues. Native comment delivery remains a separate companion-webapp release gate.

[lexdoudkin]

Production follow-up verified:

• Gateway deployment 5d6de8b7-51e5-4366-9fc0-c22c4bccd196 is ACTIVE at audited merge source 6a59266baa0ed51c4ada3c26feee953031e299aa.
• Edge version 656bda1b-8872-48d5-93b3-1d4530b85a0a exposes the fixed authenticated native routes. Real Chromium opaque-iframe requests reached all six routes with normal authentication JSON rather than fetch/CORS errors.
• Installed desktop bundle updated; normal browser OAuth reapproved; unsent question preserved without logging its content.
• Actual Figma picker shows 200 shared selectable shells/checkboxes for the first library pages, plus Search and Load more. No fetch, URL-constructor or rate-limit error is visible.
• Selected a real native Mind and verified its checkbox, then reverted the test selection. The actual current design link was copied through Figma Share and entered into board setup through the native UI.
• No Study creation, research execution or comment publication was performed. Native comments still require the separate companion webapp/provider release; this receipt does not claim that feature is delivered.

Documentation record: minds-ai-co/minds-content#404.