feat(opencode): add --since / --until date filters for daily report

[daheli]

Problem

@ccusage/opencode daily currently does not support date range filtering.

ccusage daily already supports:

• --since <YYYYMMDD>
• --until <YYYYMMDD>

But @ccusage/opencode daily --help only shows --json and --compact, so users must pipe JSON to jq for date filtering.

Why this matters

• Inconsistent UX between ccusage and @ccusage/opencode
• Harder scripting for common tasks like "last 14 days excluding today/yesterday"
• Extra dependency on jq for a very common use case

Proposal

Add these options to @ccusage/opencode daily:

• -s, --since <since> (YYYYMMDD)
• -u, --until <until> (YYYYMMDD)

Optional (nice to have):

• support ISO date input (YYYY-MM-DD) as well, with clear validation errors

Expected behavior

npx @ccusage/opencode@latest daily --since 20260211 --until 20260223

Returns only rows within the inclusive range.

Notes

Current workaround:

npx @ccusage/opencode@latest daily --json | jq '...'\n```\n\nbut built-in filtering would be much more ergonomic.