fix(agent-display): remove ZWSP sort prefixes that truncate agent names in terminals

[fr1sk]

Summary

• Set AGENT_LIST_SORT_PREFIXES values to empty strings to eliminate agent name truncation in VS Code, WezTerm, and Linux terminals
• Preserve stripping utilities (stripInvisibleAgentCharacters, stripAgentListSortPrefix) for backward compatibility with old sessions

Fixes #3418
Also addresses #3337, #3347, #3379 (same root cause)

Problem

AGENT_LIST_SORT_PREFIXES prepends 1-4 \u200B (zero-width space) characters to core agent display names for UI list ordering. Terminals that don't treat ZWS as zero-width (VS Code integrated terminal, WezTerm, Linux emulators) clip the visible agent name, producing truncated labels like ltraworker instead of Ultraworker.

Ghostty handles ZWS correctly and is unaffected.

Fix

The ZWSP prefixes are redundant — CANONICAL_CORE_AGENT_ORDER in agent-priority-order.ts already handles sorting via the order field injection. Setting prefix values to empty strings removes the visual corruption while keeping the map shape intact for callers.

Changes

File	Change
src/shared/agent-display-names.ts	Set all ZWSP sort prefix values to ""
src/shared/agent-display-names.test.ts	Update test expectations for prefix-free display names

Testing

bun run typecheck  # passes
bun test src/shared/agent-display-names.test.ts  # pre-existing test-setup failure on dev, unrelated

PR Checklist

• Code follows project conventions
• bun run typecheck passes
• bun run build succeeds
• No version changes in package.json

---

Summary by cubic

Remove zero‑width space sort prefixes from core agent display names to stop truncation in VS Code, WezTerm, and Linux terminals. Sorting now relies on the canonical order field so names render cleanly. Fixes #3418; also addresses #3337, #3347, #3379.

• Bug Fixes
  • Set AGENT_LIST_SORT_PREFIXES to empty strings for core agents.
  • Keep stripInvisibleAgentCharacters and stripAgentListSortPrefix for backward compatibility.
  • Update tests to expect prefix-free display names.

^{Written for commit 12eb7d0. Summary will update on new commits.}

[github-actions]

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[fr1sk]

I have read the CLA Document and I hereby sign the CLA

[cubic-dev-ai]

No issues found across 2 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Auto-approved: Safely removes invisible characters causing terminal truncation. Sorting logic has been moved to the order field as noted. Tests are updated to reflect the change.}