* fix(manifest): store check-in, link and tag rows as fossil does (#258)

A rebuilt or locally written repository differed from fossil's in three derived values: event and plink times in their last digits, event.omtime left NULL, and a valueless tag stored as '' instead of NULL.

Fossil stores a tag time as SQLite's julianday() bound as a double, but writes event, plink, attachment and forumpost times into SQL text with its own printf("%.17g"), which emits 16 digits in long double arithmetic. TimeToJulian is now julianday() exactly (whole milliseconds over 86400000) and TimeToTextJulian ports fossil's printf conversion, so both match fossil bit for bit. The conversion follows builds where long double is a double (macOS, Windows); fossil itself differs across platforms in the last digit.

Check-in events record omtime, tag writes bind NULL for an empty value, the readers of event and plink times under the ncruces driver rebuild the text form, and the CLI's tag listing reads NULL values.

* test(db): sweep both stored julian forms; scan the text form from driver times (#258)

* test(verify): compare text times bit for bit only where fossil computes them in double (#258) check-in: 2c2e5e74b6 user: [email protected] tags: trunk