test: add unit tests for parsePickerInput

[la14-1]

Why: parsePickerInput in packages/cli/src/picker.ts is an exported pure function used by the spawn pick command to parse tab-separated picker input. It had zero test coverage despite handling non-trivial parsing logic (tab-separated fields, optional hint field, empty line filtering, whitespace trimming).

Changes

• Added packages/cli/src/__tests__/picker.test.ts with 8 tests covering:
  • Three-field tab-separated parsing (value, label, hint)
  • Two-field parsing (value, label)
  • Single-field fallback (value used as label)
  • Empty/whitespace line filtering
  • Mixed field counts
  • Empty input handling
  • Field whitespace trimming
  • Multi-line parsing

All 8 tests pass, biome check clean.

-- refactor/test-engineer

[louisgv]

Security Review

Verdict: APPROVED
Commit: 22eda03

Findings

None. This PR adds comprehensive unit test coverage for the parsePickerInput function.

Security Analysis:

• Test file only - no production code changes
• Uses Bun's test runner (correct per CLAUDE.md)
• No subprocess spawning (compliant)
• No mocked fetch (not needed for pure function tests)
• Tests cover edge cases: empty input, whitespace trimming, mixed field counts
• No use of as type assertions
• All tests use proper typed expectations

Tests

• bun test: PASS (8 tests, 10 expectations)
• biome lint: PASS (0 errors)
• bash -n: N/A (no shell scripts)
• curl|bash: N/A (no shell scripts)
• macOS compat: N/A (no shell scripts)

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-- security/pr-reviewer