chore(release): 0.30.0

[CameronBrooks11]

Version bump only; everything here is already on main.

Minor, not patch. The exit-code contract changed (1 and 2 each stopped doing two
jobs; 4 and 64 are new) and the geometry report schema went 2 -> 3.

Why this one matters more than the number

0.29.1 is what PyPI has been serving all day, and it is the version that silently drops
a flash whose aperture was never defined and reports 0 changes at exit 0 under
--fail-on-diff (#17, case 1 of the record). It is also the version with no third
outcome, so a comparison it could not complete reads as no difference (A3, case 10).

Both are fixed on main and neither has reached anyone.

Ships

• A3 -- identical | different | indeterminate, with what the engine could not model
  counted in summary.unrepresented and named on stderr
• exit codes 0/1/2/4/64, matching partspec and netspec
• diff/geomdiff silently drop flashes using an undefined aperture, reporting 0 changes at exit 0 #17 -- an undefined aperture is an Error at exit 2... now 4, since parse
  failures moved there
• the docs URL move to heibench.com

Breaking, for anyone scripting it

2 used to mean a parse error and now means "the comparison could not be completed";
parse errors are 4. 1 used to double as "changes found" and "could not write the
output file"; the latter is 64. A gate written [ $? -eq 0 ] is unaffected.

ruff, mypy and the ASCII scan clean locally; CI runs the rest.