Add a byte budget to outline JSON

[Widthdom]

Summary

Outline can paginate hundreds of symbols but does not accept --max-json-bytes, so one page or one large symbol can exceed an AI/client response budget.

Audit IDs: Q-19. Reproduced with locally built cdidx v1.40.3 at 404db09489c305f17d94f37026e00564d3ac527a.

Existing issue relationship

No exact issue covers outline byte budgeting; this follows the repository's existing bounded-output contracts.

Expected behavior and PR scope

Outline should use the common whole-row JSON byte-budget envelope with continuation and minimum-budget diagnostics. Keep this CLI-outline-specific; MCP outline controls are separate.

Implementation guide for Codex 5.6 sol xhigh

• Measure UTF-8 bytes before committing each complete row/section and never cut JSON syntax or strings.
• Preserve hierarchy/order across page boundaries and expose total/returned/omitted/has_more/cursor.
• Return the common typed minimum-budget error when even the required envelope/row cannot fit.
• Cover large signatures, deep trees, Unicode, exact boundary bytes, array/envelope, and cursor resume.
• Add focused regression/contract tests, run the full net8.0 and net9.0 suite, and add the required bilingual changelog.d/unreleased/ fragment.

Acceptance criteria

• Output never exceeds the promised budget except for a documented typed preflight envelope.
• Truncated pages are valid JSON and resumable.
• Full unbounded outline behavior remains unchanged.

[Widthdom]

Work started on branch fix-issue4880.