qp-regress — Regression (re-run unchanged → surface_reach → delta)

Input: a baseline qp/run/<ts>/ and the same qp/plan/tcs.tsv. Output: qp/regress/<ts>/.

1. Re-run unchanged

Execute the baseline's TCs with qp-run without editing them. Editing a TC to make it pass is a new run, not a regression — say so if the user asks for it.

2. surface_reach — did the batch leave the entry screen?

bash plugins/fh-qp/scripts/qp_tools.sh surface-reach qp/run/<new-ts>/evidence.tsv

result	meaning
`REACHED n/n`	every TC observed a screen other than the modal (entry) one
`PARTIAL k/n`	some did — report which did not, by tc_id
`NOT_REACHED 0/n`	the whole batch sat on one screen (a login wall, a dead env). Every FAIL in that run is unmeasured, not a detection — write that sentence in the report
`UNMEASURED` (rc 10)	no evidence file / empty — not a zero
Denominator is all TCs, including ones that never executed; write `surface_reach.txt` with the raw line.