fix: CLI rejects negative --max-depth and --limit values

[raifdmueller]

Summary

• Issue CLI: structure --max-depth accepts negative values without error #248: dacli structure --max-depth -1 now rejects negative values with a clear error message
• Issue CLI: search --limit accepts negative values without error #249: dacli search "test" --limit -5 now rejects negative values with a clear error message
• Both follow the existing validation pattern from sections-at-level (Issue 🔧 sections-at-level cannot handle negative numbers (parsed as options) #199)

Fixes #248, Fixes #249

Changes

• Added non-negative validation for --max-depth in structure command (cli.py)
• Added non-negative validation for --limit/--max-results in search command (cli.py)
• Added 12 new tests covering both bugs (negative rejection, value in error message, zero/positive still work, aliases)
• Bumped version to 0.4.22

Test plan

• New tests verify negative values are rejected with clear error messages
• New tests verify zero and positive values still work correctly
• New tests verify aliases (str, s) also enforce validation
• Full existing test suite passes (588 tests)

🤖 Generated with Claude Code

[raifdmueller]

Code Review

Overall: Very good, no issues found

Positive

• Follows existing validation pattern from sections-at-level - good consistency
• Clear error messages include the actual value (got -5)
• Helpful hint text in error messages ("Use 0 for root level only, or omit for full depth")
• 12 tests: negative values rejected, value in error message, zero/positive work, aliases tested
• Both --max-depth and --limit/--max-results covered

Design Decision

Allowing --limit 0 (returns empty result set) is a valid choice and consistent with --max-depth 0 (returns root level only). Both are documented in the error messages.

Version Conflict

All 3 bug fix PRs bump to 0.4.22. If PRs #254 and #252 are merged first, rebase this PR and bump to 0.4.24.

Reviewed-by: R{AI}f D. Müller (AI-assisted review)