docs(obsidian-bases): date subtraction returns milliseconds, not a Duration with `.days`

Problem

skills/obsidian-bases/SKILL.md and skills/obsidian-bases/references/FUNCTIONS_REFERENCE.md still document a Duration type with .days / .hours / … fields, and formulas such as (date(due_date) - today()).days. Agents following this guidance generate .base formulas that do not match current Bases behavior.

Evidence: official docs now say milliseconds

• https://help.obsidian.md/bases/syntax ("Date arithmetic"): "Subtract two dates to get the millisecond difference between the two, for example, now() - file.ctime."
• https://help.obsidian.md/bases/syntax ("Dates and durations" section): "(now() + "1d") - now() returns 86400000 milliseconds."

I couldn't find a documented .days field on the result of date subtraction in the current docs.

Impact on agents

This is exactly the kind of error that is worse than a crash: the formula may fail only when the agent has already written several .base files, or it may be silently wrong in generated task trackers.

Proposed fix

In skills/obsidian-bases/SKILL.md:

• days_old: '(now() - file.ctime).days' → days_old: '((now() - file.ctime) / 86400000).floor()'
• days_until_due: 'if(due_date, (date(due_date) - today()).days, "")' → days_until_due: 'if(due_date, ((date(due_date) - today()) / 86400000).round(0), "")'

In references/FUNCTIONS_REFERENCE.md, replace the "Duration Type" section with a "Date differences" section:

• Subtracting two date objects returns a number of milliseconds.
• Convert explicitly (/ 86400000 for days) before using number functions such as .round(), .floor(), .ceil().
• The duration() function parses strings like "1d" for arithmetic; it does not mean date subtraction returns a Duration object.

Related

• The current .days text was introduced in merged PR #35; the official docs have since moved to millisecond subtraction.
• Closed PR #133 contained exactly this millisecond correction (e.g. ((date(due_date) - today()) / 86400000).round(0)) but was never merged.