Cloud Sync: additional bugs found during code review

[prefrontalsys]

While investigating #194, I read through the cloud sync code and found three additional bugs. Grouping them here to keep noise low.

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1. Gist search doesn't paginate — users with 100+ gists get duplicate sync gists

File: src-tauri/src/services/gist_sync.rs, line 225

let url = format!("{}/gists?per_page=100", self.api_base);

GitHub's Gist list API caps at per_page=100 with no pagination. If a user has more than 100 gists, find_or_create_gist will never find the existing sync gist and creates a new one every time "Connect" is pressed. Subsequent pushes go to an ephemeral gist that's abandoned on next connect.

Fix: Paginate using the Link header, or store the gist ID on first creation and skip the search entirely on subsequent connects.

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2. disconnect_cloud_sync sets gist ID to empty string instead of deleting it

File: src-tauri/src/commands/cloud_sync.rs, lines 129–138

let _ = db.set_setting("sync_gist_id", "");

get_sync_auth_status (line 119) checks gist_id.is_some(). If get_setting returns Some("") for empty strings, is_authenticated stays true after disconnect. The GitHub token is also left in the DB, so a re-connect reuses it without re-validating — which fails silently if the token has expired.

Fix: Delete both keys instead of setting them to empty strings, or normalize empty strings to None in the auth check.

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3. apply_pulled_payload uses wrong backup extension strategy

File: src-tauri/src/services/gist_sync.rs, line 551

let backup = path.with_extension("md.bak");

Path::with_extension replaces the existing extension rather than appending. For .md files this produces the correct result by coincidence (CLAUDE.md → CLAUDE.md.bak), but for .json files it would produce settings.md.bak instead of settings.json.bak.

The project's own utils/backup.rs handles this correctly using format!("{}.bak", file_name) with with_file_name. This code path should use the same approach.

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4. gh auth token doesn't verify gist scope

File: src-tauri/src/commands/cloud_sync.rs, line 17

gh auth token returns whatever token is stored regardless of scopes. If a user authenticated gh for Git operations only (no gist scope), the connect step succeeds but all Gist API calls return 403. The error surfaces as a generic failure message.

Fix: Use gh auth token --scopes gist or check the token's scopes against the GitHub API before storing it.

[tylergraydev]

All four bugs are now fixed.

#	Bug	Resolved by
1	Gist search doesn't paginate	511c98c — released in v3.8.3
2	disconnect_cloud_sync empty-string check	815cf4c — released in v3.8.3
3	apply_pulled_payload backup extension	1c55739, f74448e — released in v3.8.3
4	gh auth token doesn't verify gist scope	#201 — just merged, will ship in next release

Thanks for the careful review — all four were real bugs worth fixing. Closing.