v3.6.4: fix #33 — mode-aware grounding so white-box SAST findings aren't demoted

The grounding gate ran in empirical mode for every engagement, demoting
white-box (and skills/n8n audit) findings that had passed the n-model vote
because a file:line code citation isn't raw tool output. Grounding is now
mode-aware:
- Symbolic (white-box SAST / skills): a file:line reference into the reviewed
  source, or a quote of code present in it, is the receipt — no live target.
- Empirical (black-box / host / AI): evidence must resemble tool output (as before).
- Either (grey-box): a source citation OR a tool receipt grounds a finding.
The symbolic check runs against the reviewed source corpus (not the transcript)
and falls back to a structural file:line + quote check when the corpus is
unavailable. Adds unit tests incl. a regression test for #33.

neurosploit-rs/Cargo.lock

@@ -871,7 +871,7 @@ dependencies = [
 
 [[package]]
 name = "neurosploit"
-version = "3.6.3"
+version = "3.6.4"
 dependencies = [
  "anyhow",
  "clap",
@@ -888,7 +888,7 @@ dependencies = [
 
 [[package]]
 name = "neurosploit-harness"
-version = "3.6.3"
+version = "3.6.4"
 dependencies = [
  "anyhow",
  "futures",