fix(studio): prompt on unsaved changes in foreign key selector

[everettbu]

Mirror of supabase/supabase#43888
Original author: dnywh

---

What kind of change does this PR introduce?

Bug fix. Resolves FE-2802. Fixes #43882.

What is the current behavior?

Second-level foreign key side panels in Table Editor can be dismissed while dirty without a discard confirmation. That makes accidental dismissal easy and is inconsistent with the shared dirty-form dismissal pattern from FE-2802.

What is the new behavior?

• Adds DiscardChangesConfirmationDialog handling to ForeignKeySelector
• Guards all selector close paths behind a local dirty-state check
• Normalizes foreign key state so derived type metadata does not create false dirty prompts
• Clarifies in modality.mdx that route-driven/page-unload flows should use a navigation guard rather than the dialog/sheet close guard

Dirty State	Dialog

Additional context

Includes a focused unit test for foreign key dirty-state normalization.

[github-actions]

🎭 Playwright Test Results

 158 passed
 5 skipped

Details

 163 tests across 20 suites
 3 minutes, 22 seconds
 ee8f661

Skipped tests

Features › assistant.spec.ts › AI Assistant › Can send a message to the assistant and receive a response
Features › sql-editor.spec.ts › SQL Editor › snippet favourite works as expected
Features › sql-editor.spec.ts › SQL Editor › share with team works as expected
Features › sql-editor.spec.ts › SQL Editor › folders works as expected
Features › sql-editor.spec.ts › SQL Editor › other SQL snippets actions work as expected