fix: correct the pi wheel docs and comments (release review)

The gate comment in terminal-ui.js said a stale-false flag falls through
to the PageUp/PageDown fallback, which is false for pi since the second
commit of this PR removed that fallback. The FOOTGUN comment above it made
the same claim. Say what happens instead.

"Every pi below 1.0.0 emits no mouse enables" was too absolute: regular
was the default there, but fullscreen exists from 0.84.0. Measured with
--tui-mode fullscreen under tmux on 0.84.1, 0.85.0, 0.86.0 and 0.99.2:
alternate_on=1, mouse_any_flag=1, mouse_sgr_flag=1. Default settings on
0.99.2 report all 0.

Document that Wheel Scrolls Local History leaves the wheel dead in
fullscreen pi (wiki, integration guide, changeset), add a pi block to
Troubleshooting, cross-reference the accepted exception from the dead
gesture rule in architecture-invariants, and mark the pi-integration-plan
passages this PR reversed as superseded.

Comments and docs only, no runtime change.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/pi-integration.md

@@ -91,8 +91,12 @@ bypass, and project trust is a decision the person at the terminal makes.
 - **`--tui-mode`.** Which TUI you get stays your choice, in pi's `tuiMode` setting.
   Fullscreen is the default since pi 1.0.0: the wheel and clicks reach pi, and because
   Codeman strips pi's mouse enables, a drag selects text in the browser rather than
-  using pi's own selection or scrollbar drag. `tuiMode: regular`, and every pi below
-  1.0.0, is inline with terminal-owned scrollback and emits no mouse enables at all.
+  using pi's own selection or scrollbar drag. With **Wheel Scrolls Local History** on,
+  the wheel does nothing in fullscreen pi: the setting pins it to a local buffer pi
+  leaves empty, and pi has no paging fallback. `tuiMode: regular`, the default below
+  1.0.0, is inline with terminal-owned scrollback and emits no mouse enables at all. A
+  pi from 0.84.0 set to fullscreen enables mouse tracking the same way the 1.0.0
+  default does, and Codeman treats it the same.
 - **`--name`, `--no-session`, `-p`/`--print`, `--mode json`, `--mode rpc`,
   `--tools`/`--exclude-tools`, `-e`/`--extension`, `--skill`,
   `--system-prompt`.** Tracked as follow-ups in the plan doc.