_resolve_test_rel: fix absolute-py regex mis-match on tests/ prefix (fixes #1)

The absolute regex r'/[\w./-]+\.py\b' was matching the '/' inside
'tests/test_<name>.py', capturing '/test_<name>.py' instead of the
correct 'tests/test_<name>.py'.

Fix:
- Move the tests/ relative regex above the absolute .py regex so it
  matches first for any path containing 'tests/'
- Add (?<!\w) boundary guard to all three absolute-path regexes
  (/test|spec, /_test.*, /.*.py) so they only match when the leading
  '/' is at a word boundary (start of string, space, colon, etc.),
  preventing them from snatching a '/' in the middle of a relative path

Applied to running systems: boltzmann and hertz (/usr/local/bin/).

bin/bullpen-grinder

@@ -511,11 +511,11 @@ def _resolve_test_rel(body, repo):
     the grind host, but this parser only knew tests/*.py and *_test.go, so every @jsdev ticket
     was silently bounced. An absolute match fully specifies the grind — serve() derives the repo
     from its directory (2026-07-24)."""
-    m = (re.search(r"/[\w./-]+\.(?:test|spec)\.(?:js|ts)\b", body or "")   # absolute JS/TS spec
-         or re.search(r"/[\w./-]+_test\.(?:js|ts|go|py)\b", body or "")    # absolute *_test.*
-         or re.search(r"/[\w./-]+\.py\b", body or "")                      # absolute py
+    m = (re.search(r"(?<!\w)/[\w./-]+\.(?:test|spec)\.(?:js|ts)\b", body or "")   # absolute JS/TS spec (guarded)
+         or re.search(r"(?<!\w)/[\w./-]+_test\.(?:js|ts|go|py)\b", body or "")    # absolute *_test.* (guarded)
+         or re.search(r"tests/[\w./-]+\.py", body or "")                          # tests/ relative py
+         or re.search(r"(?<!\w)/[\w./-]+\.py\b", body or "")                     # absolute py (guarded)
          or re.search(r"[\w./-]*(?:\.test|\.spec|_test)\.(?:js|ts)\b", body or "")  # relative JS/TS
-         or re.search(r"tests/[\w./-]+\.py", body or "")
          or re.search(r"[\w./-]+_test\.go", body or ""))
     if m:
         return m.group(0), None