feat(calendar): add --sort / --order for events listing

[gado-ships-it]

Summary

gog calendar events --all aggregates events from every calendar, but the result comes back in CalendarList iteration order (one calendar's events as a block, then the next). That makes the merged view unusable for agents/humans who want a single chronological list across calendars — the original motivation here was planning "today from now on" via an LLM agent.

This PR:

• Adds --sort=start|end|summary|calendar and --order=asc|desc to calendar events. With --sort=start, events from all calendars interleave by absolute instant (parsed through the existing parseEventTime / parseEventDate helpers so RFC3339 with offset, RFC3339Nano, and all-day 2006-01-02 dates compare correctly across timezones).
• Documents now in the --from / --to help strings for both calendar events and the shared TimeRangeFlags. timeparse.ParseRangeExpr already resolves now, but the help only listed today, tomorrow, monday, so the precise "from this instant onward" form was invisible to anyone reading --help.
• Removes an unused wrapEventsWithTimezone helper that lost its only call site after the JSON path was restructured to share wrapping with the table path.

Default sort is empty so existing behavior is unchanged; the help string flags start as the recommended value with --all.

Example (placeholder data):

$ gog calendar events --all --from=now --sort=start --max=5 -p
CALENDAR     ID   START                       END                         SUMMARY
work-cal     ...  2026-05-13                  2026-05-14                  All-day deadline
personal-cal ...  2026-05-14T16:00:00Z        2026-05-14T16:30:00Z        Standup
team-cal     ...  2026-05-15T09:00:00+02:00   2026-05-15T17:00:00+02:00   Offsite
holidays     ...  2026-05-18T10:30:00Z        2026-05-18T11:00:00Z        Workshop

Test plan

• make fmt clean
• make lint clean (no new issues)
• make test green
• New TestListAllCalendarsEvents_SortByStart covers --sort=start --order=asc + --order=desc against a two-calendar fixture where the API returns late before early.
• New TestSortEventsBy_Summary covers case-insensitive summary sort + reverse.
• Smoke-tested live against a multi-calendar Google account spanning personal, team, and holiday calendars: events interleave correctly across +02:00, Z, and all-day formats.

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