Log real-world road test results and correct/extend the CO-trim theory

New research/ROAD_TEST_LOG.md: the 2026-09-15 flash of
20262-arrow-delete-lowthrottle-composed.hex was a major real-world
success (stalling fully resolved, decel backfire much reduced but not
eliminated). Captures the live diagnostic reasoning that followed:
correcting an overly-lean-leaning framing mid-session (residual decel pop
is more likely a rich-unburned-mixture-with-no-SAI-assist problem, not a
lean one), a structural hypothesis that the Idle Fuel Trim (CO) curve
likely applies whenever the throttle is closed at any RPM rather than
only at a literal stop (only 2 of its 32 points are currently corrected,
and the untouched middle range lines up with the residual pop's RPM
window), and the reasoning for rejecting airbox-baffle removal as a fix
for decel popping specifically (wrong mechanism -- closed throttle isn't
airbox-limited -- and risks worsening the separately-flagged, still
unaddressed main-VE-table leanness gap).

Also updates TABLES.md with the CO-trim applicability open question, and
brings TUNING_GUIDE.md's "local research assets" section up to date (it
still said maps were gitignored/unflashable, both stale).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FP2GaxS9HkUdL5sLBnjKje

tunie/research/reference-maps/TABLES.md

@@ -133,6 +133,25 @@ Composing two independent tunes' curves here needs the same per-cell
 arithmetic treatment as the main VE tables (`PERMUTATIONS.md`), not a
 handful of spot fixes.
 
+**Open question, raised from real-world testing (2026-09-15/16, see
+`../ROAD_TEST_LOG.md`): does "idle" in this table's name mean literal
+engine-stopped idle, or does it apply whenever the throttle is
+closed/near-closed regardless of RPM?** TuneECU's own docs say "at idle,"
+but the table has real, non-trivial entries all the way out to 10,000 RPM
+— hard to explain if it only ever applied near a stop. Circumstantial
+support for "applies whenever throttle is closed": a real-world decel
+sweep through the *uncorrected* middle of this curve (RPM 2600-6500,
+composed only touched points 2400 and 7000) produced residual popping in
+exactly that RPM range, while the low-throttle table fix (a genuinely
+different, confirmed-idle-adjacent table) independently and completely
+fixed literal stopped-idle stalling. That's consistent with this curve
+being live during the whole closed-throttle deceleration, not just at a
+stop — but it's inference from one road test, not confirmed in the
+decompile. Worth designing a deliberate test for if this gets revisited:
+does the CO Trim value visibly change on TuneECU's live-diagnostics screen
+while decelerating at 4000 RPM with the throttle shut, or only once RPM
+actually reaches idle?
+
 ## SAI / O2 / lambda flags
 
 Now findable via the localised flat-ROM diff (20187 vs 20188), which isolates small