fix(tracing): align _correlate_business to opt-out semantics (default on)

Match sgp_obs env_off: disable ONLY on an explicit {0,false,no,off}; unset,
empty, or an unrecognized value stays ON. Adds "off" to the token set and stops
treating an unrecognized value as True-by-coincidence — now it's True by rule
(opt-out), so a typo can't silently drop correlation. Test covers off-tokens +
empty/typo staying on.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: NiteshDhanpal

src/agentex/lib/core/tracing/trace.py

@@ -50,11 +50,14 @@ def _obs_mode() -> ObsMode:
 
 
 def _correlate_business() -> bool:
-    """``SGP_OBS_CORRELATE_BUSINESS`` — default True. Read from the env directly
+    """``SGP_OBS_CORRELATE_BUSINESS`` — OPT-OUT: defaults True, disables ONLY on an
+    explicit {0, false, no, off}. Unset, empty, or an unrecognized value (a typo)
+    stays ON, so correlation is never silently dropped. Read from the env directly
     (mirroring ``_obs_mode``) rather than sgp_obs.TracingConfig, so we don't depend
-    on a specific config-field surface. When false, the Correlator opens the obs
-    span but writes NO business<->obs correlation in either direction."""
-    return (os.getenv("SGP_OBS_CORRELATE_BUSINESS") or "true").strip().lower() not in ("false", "0", "no")
+    on a specific config-field surface; the off-token set matches sgp_obs ``env_off``.
+    When false, the Correlator opens the obs span but writes NO business<->obs
+    correlation in either direction."""
+    return (os.getenv("SGP_OBS_CORRELATE_BUSINESS") or "").strip().lower() not in ("0", "false", "no", "off")
 
 
 def _build_correlator() -> Correlator:

tests/test_correlate_business_passthrough.py

@@ -13,13 +13,15 @@
 
 def test_correlate_business_env_parsing(monkeypatch):
     monkeypatch.delenv("SGP_OBS_CORRELATE_BUSINESS", raising=False)
-    assert _correlate_business() is True  # default on
-    for falsey in ("false", "0", "no", "FALSE", " no "):
+    assert _correlate_business() is True  # unset -> on
+    # explicit recognized off-tokens -> off (matches sgp_obs env_off)
+    for falsey in ("false", "0", "no", "off", "FALSE", "Off", " no "):
         monkeypatch.setenv("SGP_OBS_CORRELATE_BUSINESS", falsey)
-        assert _correlate_business() is False
-    for truthy in ("true", "1", "yes", "", "anything"):
+        assert _correlate_business() is False, falsey
+    # on-tokens AND empty / unrecognized (a typo) -> stays ON, never silently off
+    for truthy in ("true", "1", "yes", "on", "", "   ", "ture", "garbage"):
         monkeypatch.setenv("SGP_OBS_CORRELATE_BUSINESS", truthy)
-        assert _correlate_business() is True
+        assert _correlate_business() is True, repr(truthy)
 
 
 def test_build_correlator_never_crashes():