draft: feat: Edit connector

[royendo]

Adds a visual editor for connector YAML files (VisualConnector.svelte) and an edit flow for existing connectors from the file
explorer.

• Visual connector workspace: Connector files now open a form-based editor (matching the "Add connector" modal UI) instead of a
  raw code editor by default. Supports save, revert, error display, and a code toggle for the raw YAML.
• Edit connector from nav: Right-clicking a connector in the file explorer shows an "Edit connector" option that opens the modal
  pre-filled with existing values (secrets resolved from .env).
• Save without Test and Connect: Adds a Save button to the modal that writes the connector YAML and .env without testing the
  connection, then waits for the runtime to parse the file before navigating so the workspace opens with correct values.
• Edit mode in modal: AddDataForm gains an editMode prop — in edit mode, the form pre-loads the existing connector's values and
  Save updates in-place without navigating.

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!