Fix reDUP CLI check exit status when duplicate budgets are exceeded #20

Parent wellmanifest/PLF-002: backlog intake from regression verification; no competing implementation writer is started. Canonical result: https://github.com/subactor/docs/blob/b80c27e6d4c8caa0c6db389eddb4377d9f86cd8a/architecture/analysis/wellmanifest-standards-harmonization.md .

Reproduced at semcod/redup source827418a798d9a5d4d455ffc7e4228e7d063c106f (editable install metadata0.4.31, source VERSION0.4.48): redup check src --ext .py --min-lines 10 --min-sim 0.80 --max-groups 0 --max-lines 0 exits0 on frozen wellmanifest/metafile310a9dc1f71c16b10b02204f03bdc4c5d88c109f while reporting15files/2062lines/94groups/1152recoverablelines. cli_app/main.py promises threshold enforcement, but scan_commands.check_command only slices printed groups and never raises on exceeded budgets. Receipt comparison SHA256 9df70274f3c5762b114acf14b62f2938e64b624d42fc412092f0e71bf4897940.

Acceptance: enforce explicit/default group and recoverable-line budgets independently of display; meaningful CLI negative fixture exceeds each budget and exits nonzero; equality/zero-duplicates pass; reject invalid budgets; preserve scan/report and existing MCP checks. Add CLI regression coverage using actual invocation. Keep current Metafile/Reuse published heads and protected review requirements frozen. Source implementation requires its own allocated native ticket, canonical worktree and fenced lease; this request grants no runtime or policy bypass.

Strategy Metadata:

• repository: semcod/redup
• planfile_id: semcod/redup:3bf056a35590b4a0:PLF-022

Parent wellmanifest/PLF-002: backlog intake from regression verification; no competing implementation writer is started. Canonical result: https://github.com/subactor/docs/blob/b80c27e6d4c8caa0c6db389eddb4377d9f86cd8a/architecture/analysis/wellmanifest-standards-harmonization.md .

Reproduced at semcod/redup source827418a798d9a5d4d455ffc7e4228e7d063c106f (editable install metadata0.4.31, source VERSION0.4.48): redup check src --ext .py --min-lines 10 --min-sim 0.80 --max-groups 0 --max-lines 0 exits0 on frozen wellmanifest/metafile310a9dc1f71c16b10b02204f03bdc4c5d88c109f while reporting15files/2062lines/94groups/1152recoverablelines. cli_app/main.py promises threshold enforcement, but scan_commands.check_command only slices printed groups and never raises on exceeded budgets. Receipt comparison SHA256 9df70274f3c5762b114acf14b62f2938e64b624d42fc412092f0e71bf4897940.

Acceptance: enforce explicit/default group and recoverable-line budgets independently of display; meaningful CLI negative fixture exceeds each budget and exits nonzero; equality/zero-duplicates pass; reject invalid budgets; preserve scan/report and existing MCP checks. Add CLI regression coverage using actual invocation. Keep current Metafile/Reuse published heads and protected review requirements frozen. Source implementation requires its own allocated native ticket, canonical worktree and fenced lease; this request grants no runtime or policy bypass.