--top <n> flag to cap table rows

[dchaudhari7177]

report/skills/agents/cost printed every row. --top <n> caps them.

Behaviour

• Caps after the sort, so it keeps the highest-ranked rows under whatever --sort is active (--sort name --top 3 gives the first three alphabetically, not the top three by fires).
• Unlimited when omitted — current behaviour is untouched.
• n is validated as a positive integer, following the existing --sort validation pattern: --top 0, --top 2.5, --top ten and --top=-3 all exit 2 with --top expects a positive integer.

Consistency across formats

Rather than capping inside each of the four renderers (easy to let one drift), the cap is applied to the Report itself — used/untracked/dead are sliced in one capReport helper that every format then renders. Terminal, json, md and csv therefore cap identically by construction. The --dead and --untracked row paths are capped too.

Applied to cost as well as report/skills/agents, since it is the same kind of component table and the flag surface is shared — happy to drop that if you'd rather keep it off cost.

Tests

New test/top.test.ts drives a synthetic four-row Report (same approach as sort.test.ts, since the fixture history only has one component so a cap can't be observed there): caps post-sort, caps after rather than before sorting, defaults to unlimited, is a no-op when n exceeds the row count, caps identically in all four formats, and applies to report. Flag validation is covered in test/cli.test.ts.

Typecheck and the full suite (89 passing) are green.

Closes #31

[notsointresting]

Conflict against main now — a few other PRs touching src/cli.ts/themes/index.ts landed first. Could you rebase onto main and resolve? Should just be re-applying your change alongside the others already merged.