fix(md): --all should emit the whole page instead of stopping at the default budget

[kiakiraki]

Problem

--md always passes budget: opts.budget || 2000 to emitLines, and cap() in
src/lib/emit.ts only skips --limit when --all is set — the budget is applied
either way. So --md --all is still cut at ~2000 tokens, and the truncation note
points the user at --all, which is already set:

$ ax big.html --md --all | grep -c 'paragraph number'   # page has 300 paragraphs
121
$ ax big.html --md --all 1>/dev/null
ax: note: 357 more result(s) hidden — continue with --offset 242 (or --all, --limit N, --budget T)

Every other mode (--row, --table, --text, --outline) emits everything under
--all; --md was the only asymmetric one. The only way to read a long page in
full was to guess a large explicit --budget.

Fix

Treat the 2000 tokens as a default, not a floor — src/commands/root.ts:

const budget = opts.all || opts.budget > 0 ? opts.budget : 2000
return emitLines(md.split('\n'), { ...opts, budget })

• --all → no budget, whole page (and no note claiming something is hidden)
• explicit --budget T → T wins, as on every other path through cap()
• neither → unchanged, ~2000 tokens

--help now states the default on the --md line, since it is conditional.

I did not make cap() ignore the budget when --all is set: --all (drop the
result-count cap) and --budget (token ceiling) are orthogonal, and that change
would silently alter --row --all --budget T for every mode.

Verification

300 paragraphs of ~60 chars:

command	before	after
--md --all	121 paragraphs + 357 more result(s) hidden	300 paragraphs, no note
--md	25 paragraphs (--limit 50)	unchanged
--md --all --budget 200	12 paragraphs	unchanged (explicit budget respected)

Tests

Two cases in test/cli.test.ts (147 pass, oxfmt --check and tsc --noEmit clean):

• --md --all emits the whole page with no note, and --all --budget 200 still truncates
• --md alone stays capped by the default budget — long-prose fixture whose line count
  never reaches --limit 50, so a regression that drops the default would fail here

🤖 Generated with Claude Code

[yusukebe]

LGTM!

[yusukebe]

@kiakiraki This is an actual bug. Nice fix. Thanks!