Add ISO ordinal and week-date parsing

[brickfrog]

Closes tempo-bra.4.\n\nAdds strict Date::parse_ordinal and Date::parse_iso_week parsers that mirror the existing format_ordinal and format_iso_week outputs for 4-digit years. Both parsers reuse the existing Date constructors for calendar validation and reject malformed input, trailing characters, and out-of-range ordinal/week fields.\n\nVerification:\n- moon fmt --check\n- moon test --target wasm-gc\n- moon test --target js\n- moon test --target native

Verification

Generated by Choir from commands executed in the leaf workspace.

• moon fmt --check
  • exit: 0
  • head: 2929759
  • output tail:

Finished. moon: no work to do

• moon test --target wasm-gc
  • exit: 0
  • head: 2929759
  • output tail:

Total tests: 288, passed: 288, failed: 0.

• moon test --target js
  • exit: 0
  • head: 2929759
  • output tail:

Total tests: 288, passed: 288, failed: 0.

• moon test --target native
  • exit: 0
  • head: 2929759
  • output tail:

Total tests: 288, passed: 288, failed: 0.

[brickfrog]

Choir: GitHub Actions rollup reports all checks successful on the latest head — re-check review/merge policy on GitHub (not an approval or merge signal by itself).

[Copilot]

Pull request overview

This PR adds strict ISO 8601 parsing helpers for ordinal dates and ISO week-dates, aligning with the library’s existing formatting helpers for 4-digit years and using existing Date constructors to validate calendar correctness.

Changes:

• Add Date::parse_ordinal("YYYY-DDD") and Date::parse_iso_week("YYYY-Www-D") with full-input consumption (no trailing characters).
• Add unit tests covering valid round-trips and malformed/out-of-range rejection for both parsers.
• Expose the new public APIs in the generated package interface.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/tempo.mbt	Adds the two new strict date parsers that delegate validation to existing Date constructors.
src/tempo_test.mbt	Adds round-trip and rejection tests for ordinal and ISO week-date parsing.
src/pkg.generated.mbti	Publishes the new parser functions in the package’s generated public surface.

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[brickfrog]

Choir: comment-only review received — routed to main.ergo-task-add-iso-8601-1780418501483-596086 (leaf pane).

[brickfrog]

Choir: GitHub Copilot issue-thread comment observed on PR — parent notified with updated gate snapshot (not merge approval).

[brickfrog]

Choir: comment-only review received — routed to main.ergo-task-add-iso-8601-1780418501483-596086 (leaf pane).

[brickfrog]

Choir: fixes pushed by main.ergo-task-add-iso-8601-1780418501483-596086 — resolving threads and checking gates (not merged yet).

[brickfrog]

Choir: GitHub Actions rollup reports all checks successful on the latest head — re-check review/merge policy on GitHub (not an approval or merge signal by itself).