fix: stop resetting an emptied custom agent id mid-typing

[RAIT-09]

Description

Retyping a custom agent's ID was nearly impossible: the moment the field went empty (deleting the last character), the per-keystroke onChange regenerated the default id (custom-agent) and wrote it straight back into the input. Deleting custom-agent character by character snapped back to custom-agent on the last backspace — the only workaround was select-all-and-overwrite.

The repair logic itself is legitimate (ids are keys — section open-state, defaultAgentId retargeting, and every keystroke persists via flushSettings() — so settings must never hold an empty id), but it ran at the wrong time. The same field already established the right timing for exactly this reason: the preset-collision check validates on blur, with a comment noting that per-keystroke validation misfires because onChange commits every intermediate value.

This PR moves the empty handling to the same model:

• onChange skips empty values entirely. An empty field is a transient state while retyping; settings keep the last valid id, so the "no empty id in settings" invariant is now guaranteed by never committing one rather than by regenerating.
• Blur restores an abandoned-empty field. Since settings always hold the last valid id, the field just gets it back — no regeneration, no rekey, no save. The restore falls through to the existing preset-collision check, so the edge case "type a reserved preset id (committed), select-all delete, blur" still gets the suffix-rename repair.

The Display name field is deliberately left unchanged: its blank-means-fallback model suits a derived cosmetic value, while an identity key that is referenced elsewhere (fence agent: pins, saved sessions, per-agent last-used maps) should conservatively restore rather than silently swap to a generated default.

Related issue

None (reported during manual testing).

Type of change

• Bug fix
• New feature
• Documentation
• Refactor
• Other

Checklist

• npm run lint passes ("Use sentence case for UI text" errors are acceptable for brand names)
• npm run build passes
• Tested in Obsidian
• Existing functionality still works
• Documentation updated if needed (no docs describe the old reset behavior)

Testing environment

• Agent: N/A (settings tab input handling only). Verified: deleting an id character by character no longer snaps back, abandoning an empty field restores the last valid id on blur, the preset-collision repair still fires after an empty-field blur, open sections survive renames, and the default agent follows a rename
• OS: macOS

Screenshots

N/A

Summary by CodeRabbit

• Bug Fixes
  • Improved custom agent ID editing by allowing the field to remain temporarily empty while typing.
  • Prevented unintended ID changes when an empty value is abandoned.
  • Restored the last valid custom agent ID when leaving the field without entering a replacement.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 9acfb304-e028-4d9f-86d5-2b6492141d55

📥 Commits

Reviewing files that changed from the base of the PR and between 28a4265 and 5f3b54d.

📒 Files selected for processing (1)

• src/ui/SettingsTab.ts

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📝 Walkthrough

Walkthrough

Custom agent ID editing now treats empty input as a transient state, preserving the committed ID until a non-empty value is entered and restoring it when the field loses focus.

Changes

Custom agent ID editing

Layer / File(s)	Summary
Empty ID editing and blur restoration src/ui/SettingsTab.ts	Empty changes no longer commit generated IDs or rekey state; blur restores the last committed ID before the existing collision and rename flow.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• RAIT-09/obsidian-agent-client#350: Both changes update custom agent ID rekeying and open-section handling in src/ui/SettingsTab.ts.

Suggested reviewers: donivatamazondotcom

Poem

I cleared the field, then paused my hop,
The saved ID stayed safely atop.
No phantom name was born anew,
Blur brought back the value true.
A tidy setting, bright and neat! 🐇

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise and accurately describes the main behavior change to custom agent ID editing.
Description check	✅ Passed	The description follows the template and includes the change summary, issue, type, checklist, testing environment, and screenshots status.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/custom-agent-id-typing

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