Harden Gmail delete flow and sort selection handling

[ZingBing]

Fixes #81

Summary

This PR hardens Gmail delete automation to be safer and more reliable across both normal and bulk delete flows, including Gmail AI sort variations and asynchronous bulk-delete toasts.

What Changed

Delete flow safety and scope control

• Added strict search-scope checks so destructive actions only run when the expected query is active.
• Added query helpers to build and validate expected from:(...) search scope.

Sort behavior (Most recent)

• Added best-effort _ensureMostRecentFilter() logic:
  • If sort controls are present, attempts to switch to Most recent.
  • If controls are absent (e.g. non-AI Gmail), logs and continues without blocking deletion.

Bulk vs non-bulk handling

• Unified delete execution into a single flow that:
  • Selects current-page results
  • Detects optional Select all conversations... banner
  • Only attempts bulk-confirm dialog handling when bulk selection is actually used
• Bulk confirm detection targets the correct Gmail dialog structure (dialog/alertdialog, data-mdc-dialog-action="ok").

Success detection (toast handling)

• Improved delete confirmation detection to support both:
  • Standard success toasts (moved to Trash/Bin)
  • Async bulk toasts (e.g. “remaining conversations in a few minutes”, “might take longer”)
• Uses both mutation observation and polling to reduce missed toast updates.

Error behavior

• Missing critical controls now fail explicitly (e.g. visible Delete button not found).
• Prevents false success when key destructive steps did not actually execute.

Why

Previously there were two opposite failure modes:

• False success when deletion did not fully apply.
• False error when deletion succeeded but toast/confirmation detection missed variant Gmail messaging.

This PR keeps strict safety checks while improving practical reliability of user-facing success/error status.

Testing Notes

Manually tested in Gmail:

• Non-bulk delete (single-page results): delete + success path.
• Bulk delete (with Select all conversations...): confirm dialog + async toast variant.
• Sort control on Most recent vs Most relevant.
• Sort control fallback behavior remains non-blocking.

Notes

• No UI component changes; behavior changes are in content-script service logic.
• package-lock.json was not included in this PR.
• I added some safety guards because I accidentally bulk deleted my entire inbox when testing... whoops

[ZingBing]

As an additional note, this PR may also address #82 (the deleting portion, unsubscribe has not been addressed) and #73. I can look into the errors from 73 but this PR changes the way bulk deletes are handled.

@anna-st-40 Would you or copilot be able to review this PR? I believe it would help the overall functionality of the extension.