fix(hygiene): untrack .coverage — the verdict command was rewriting a tracked binary

.gitignore

@@ -103,6 +103,34 @@ venv/
 .mypy_cache/
 .ruff_cache/
 
+# --- coverage data: build output, regenerated by every `verify.py --coverage` run ---
+# `.coverage` was TRACKED from #109 until 2026-08-24 -- a 90 KB opaque SQLite database that arrived
+# as a side effect of a typing PR whose title, body and every other changed file are about mypy.
+# Nobody chose to commit it; it was in the working tree when the branch was staged, which is the
+# same accident that put src/UNKNOWN.egg-info/ on PR #113 one section above -- there the autofix
+# bot was identified as the stager, here the stager is not recorded either way.
+#
+# It is pure build output, and the churn is mechanical rather than occasional: verify.py's
+# coverage_reset() UNLINKS ROOT/.coverage and ROOT/.coverage.* before every instrumented run, then
+# coverage_combine_and_report() writes them again. So while tracked, `verify.py --coverage` shows up
+# as a DELETION of a tracked binary followed by a re-add of different bytes, and any uncommitted
+# copy blocks a branch switch.
+#
+# BOTH patterns, because two different steps write them and ignoring only the combined file leaves
+# one data file PER INSTRUMENTED CHILD unignored -- `--parallel-mode` writes
+# `.coverage.<host>.<pid>.<random>` for each of ~90 subprocesses, and `coverage combine` merges them
+# into `.coverage`.
+#
+# `/.coverage.*` and NOT `/.coverage*`: the second also swallows `.coveragerc`, coverage.py's own
+# config file, which is source. Bounding by "starts with .coverage" is the too-broad-by-kind failure
+# the langsmith patterns above record.
+#
+# ROOT-ANCHORED per the rule #72 established for every debris pattern in this file, and true for the
+# same reason here: verify.py globs and unlinks ROOT, so the checkout root is the only place these
+# land. Deliberately ABOVE the template-managed block, which a Template-Version bump rewrites.
+/.coverage
+/.coverage.*
+
 # --- lock and backup artifacts ---
 *.lock
 *.bak