Check 2 flagged 'N consecutive same-size shots' from a count of every equal
adjacent pair across the whole plan, not the length of any real run. So three
separate 2-shot groups (wide,wide,cu,cu,med,med) tripped a false '3
consecutive' violation, while a genuine run of 3 (only 2 pairs) was never
flagged. Track the current run length, reset on change, and compare the longest
run >= 3.
Adds regression tests: non-consecutive pairs pass, a true run of 3 is flagged,
unspecified shots don't form a run.
Closes#268
364182cc39