fix: restore destination dates + free-cancellation flags lost by a stacked merge

[akoso]

Recovers commit 069ecbc — reviewed and approved in #2, but never actually delivered to main. Cherry-picked cleanly onto current main, unmodified, original authorship preserved.

What happened

#2 was a stacked PR: its base was fix/cli-from-json-and-login-bugs (the branch of #1), not main. #1 merged into main first (9a43adc), and #2 then merged into that already-merged branch. The merge commit exists, GitHub shows #2 as MERGED, and the feature commit is nonetheless not an ancestor of main:

$ git merge-base --is-ancestor 069ecbc origin/main   # → false

#3's skill docs did reach main (rebased, as 450e70e), so the documentation for this feature landed while the feature itself did not.

Why this matters now — it's a release blocker

skills/mna/SKILL.md and skills/mna/references/cli-and-schemas.md on main today instruct Claude to run:

mna destinations add <trip> <var> --place "…" --start-date <YYYY-MM-DD> --end-date <YYYY-MM-DD>
mna options edit … --free-cancellation-until <date>

None of those flags exist on main. citty does not reject unknown flags, so the dates are silently dropped — the write returns 2xx and the trip is quietly missing its dates. That's precisely the silent-drop failure the skill's own "verify-after-write" section warns about, and the skill is shipped inside the npm tarball, so it would go out with the first release.

This also explains a second symptom: the committed openapi.json snapshot has been lagging production. 069ecbc re-synced it, and that re-sync was lost with it.

What the commit contains

• --start-date / --end-date on destinations add and edit, accepting YYYY-MM-DD or a full ISO date-time, normalized to UTC start-of-day and mapped to startDate / endDate.
• --free-cancellation-until on options add / edit (accommodation only, with a clear error otherwise). For options edit it also makes --from-json optional, so updating just the date no longer needs a JSON file.
• Shared helpers util/dates.ts and commands/options/free-cancellation.ts, both unit-tested, plus command-level flag→body mapping tests.
• Re-syncs openapi.json with the live production surface.

Verification

bun install       ✓
bun run codegen   ✓
bun run typecheck ✓  clean
bun run lint      ✓  92 files, 0 errors
bun test          ✓  34 pass / 0 fail  (was 22 on main)

Confirmed the flags are now real (destinations add --help shows --start-date / --end-date; options edit --help shows --free-cancellation-until and an optional --from-json), and that after this commit the committed snapshot regenerates byte-identical to production — the drift is gone.

Relationship to #4

Independent. #4 is the @mantacode/mna-cli rebrand and packaging prep and deliberately touches no source. Either can merge first; there are no overlapping files. Merging both before the first tag is what makes the shipped skill honest.