ci(coverage): raise the parse-partial ceiling to 59, for a gap main added (#963)

The gate's check 4 failed on its own pull request: parse_partial_count is 59
against a ceiling of 58. The rise did not come from this branch.

Measured with the binary built from this branch, three trees indexed:

  this branch, no merge      58   matches the baseline as written
  origin/main alone          59
  main merged into it        59   identical file list to main alone

CI tests the merge of a pull request into main, so the gate sees 59. The one
file main added to the flagged list is src/daemon/runtime.c, at one line:

  src/daemon/runtime.c   47-47   1 line of 3291   0.03% of the file

Line 47 is a function-style _Atomic declaration:

  static _Atomic(cbm_daemon_runtime_containment_hook_t) runtime_containment_hook_seam;

The tree-sitter C grammar does not parse that form. The keyword form four
lines above it, `static _Atomic uint32_t ...`, parses fine. This is the same
class of grammar limitation this branch already pins for _Thread_local in
tests/test_parse_coverage.c. It arrived with fc1b1ee on main.

So the ceiling moves to 59 rather than the file being allowlisted. An
allowlist entry is for a file whose single range is over the 25% limit and
has a written reason to stay; one line out of 3291 is nowhere near it, and
hiding the file would remove a real gap from the count the ceiling exists to
watch.

Known cost, worth stating plainly: a ceiling checked against a moving main
drifts. Any merge to main that adds a partially-parsing file reddens every
open pull request until someone edits this file by hand, and the pull request
that goes red is never the one that caused it. This commit does not fix that
- the fix is to compare against the merge base instead of a checked-in number,
which changes what the gate is and belongs to whoever owns CI policy here.
Filed separately.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Signed-off-by: Joshua Richter <jrichter5781@gmail.com>

Author: CaptainMittens

scripts/ci/parse-partial-baseline.txt

@@ -4,4 +4,8 @@
 # in tests/test_index_resilience.c, which stops the signal being switched off
 # by accident. Raising this number is allowed but should be explained in the
 # commit that does it.
-58
+#
+# 58 -> 59 on 2026-08-31. main gained src/daemon/runtime.c, whose line 47 the
+# tree-sitter C grammar cannot parse. The rise came from main, not from a
+# branch. See the commit for the measurement.
+59