fix(playground): use contextual untitled filenames

[omribz156]

Summary

• Generate Query Playground untitled filenames from the tree node context, e.g. {cluster}_{collection}.documentdb.js or {cluster}_{database}.documentdb.js.
• Sanitize invalid filename characters and whitespace before building the filename.
• Add numeric suffixes when a contextual playground filename is already open, while preserving the existing generic fallback when no context is available.

Closes #660

Verification

• npm run build
• npm run lint -- src/commands/playground/newPlayground.ts src/commands/playground/newPlayground.test.ts
• npm run jesttest -- src/commands/playground/newPlayground.test.ts --runInBand
• npm run prettier -- src/commands/playground/newPlayground.ts src/commands/playground/newPlayground.test.ts
• npm run l10n
• npm run package
• git diff --check

This was implemented with Codex assistance, with the patch kept focused and manually reviewed before sending.

[Copilot]

Pull request overview

This PR updates Query Playground creation to generate context-aware untitled filenames (derived from the originating tree node), improving tab readability when multiple playgrounds are open.

Changes:

• Pass cluster + database/collection context into playground creation when launched from the tree.
• Add filename generation that sanitizes invalid characters/whitespace and appends numeric suffixes on collisions.
• Add Jest unit tests for contextual naming, sanitization, suffixing, and fallback behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/commands/playground/newPlayground.ts	Adds contextual filename generation + sanitization/suffix logic and wires it into playground creation from tree context.
src/commands/playground/newPlayground.test.ts	Adds unit coverage for the new filename generation behavior.

[tnaum-ms]

Two maintainer follow-up commits pushed to this branch:

721c40d fixes two collision gaps in createPlaygroundFileName: the generic playground-N fallback used a raw document count as the suffix, which could collide after closing a middle playground (e.g., closing playground-2 leaves [-1, -3] open and the old logic would re-issue playground-3). Also addresses the Copilot review comment by broadening the dedup set to all open text documents. Both the contextual and generic branches now share a single find-next-free-name loop.

4fef0c9 pipes context through newPlaygroundWithContent (the entry point used by Collection View and the Interactive Shell). Those playgrounds now get contextual cluster_database.documentdb.js names instead of falling back to playground-N.

[tnaum-ms]

Hey @omribz156, thanks for this contribution!

The core idea is solid and the test coverage was a great addition.

We made a few follow-up tweaks on top:

The collision check now covers all open text documents (not just playground-language ones), since VS Code rejects applyEdit on a duplicate URI regardless of language mode. The generic playground-N fallback also got the same loop-based approach so it can't collide after a user closes a middle playground.

newPlaygroundWithContent (the cross-feature entry point from Collection View / Interactive Shell) now also produces contextual filenames, since it already had the cluster and database name available.

Minor parameter cleanup: the filename context is now derived directly from the connection object instead of being passed as a separate parameter with duplicated fields.

All changes are on this branch as individual commits, so the history stays readable. Thanks again!