fix: workspace view search param collides with explore view=pivot and blanks the editor

[nishantmonu51]

Opening an explore file sometimes rendered neither the code editor nor the preview, with no console or network errors. The workspace body was empty because the persisted workspace view was pivot.

• An explore previewed inside a file workspace writes its URL state onto the file route, including view=pivot / view=tdd. The files route's consumeViewSearchParam treated that as the workspace view, persisted it to localStorage, and ExploreWorkspace has no branch for it. The bad value survived reloads and restarts until the header toggle was clicked.
• Rename the workspace view search param from view to editor so it cannot collide with the explore's own view param. All links go through getFileHref, so no other call sites change.
• Only accept known workspace views from the param and from localStorage.
• ExploreWorkspace now treats any non-code view as the preview, so users who already have a stale pivot/tdd value stored recover on next load.
• Added workspace-stores.spec.ts covering the localStorage fallback and the param handling.

Repro before the fix: open an explore file, switch to the visual editor, click "Start Pivot", then reload or navigate away and back.

Closes APP-934

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• Intend to cherry-pick into the release branch
• I'm proud of this work!