Settle a Generation 1 script branch on a byte with a closed set

[Decryptu]

wSpritePlayerStateData1FacingDirection holds one of four values and wRivalStarter and wPlayerStarter one of three. A cp against a value the walk has already excluded cannot match, and one the set has nothing else left beside always does, so both unknown arms of the text_asm corpus on Red and Blue are gone.

Fixed

• GateUpstairsScript_PrintIfFacingUp re-tests a facing its caller's jp nz has already refused, so Route 11 Gate 2F's left binoculars row no longer carries an unreachable arm.
• Route22GetRivalTrainerNoByStarterScript's cp b loop walks a three-row table with no terminator and unrolled into the code behind it. 12 starter nodes and 8 trainer_battle rows of the map state census were bytes rather than table rows.
• The hidden event census doc in tools/checks/gen1_maps.gd sat above _elevators.

Removed

• Gen1WorldImporter.decode_script's refused parameter, which no caller passed, and the six sites that appended to its list.

tools/validate.gd -- all passes 94 topics on all six cartridges; the unit tier's 1293 gen1 and world tests pass and two new cases in tests/unit/test_gen1_script.gd cover both settled shapes.