feat(docs): add CLASSIFICATION function-header field, rename history shadow

Rename the C1 history() shadow to pretty-history so it never collides
with the fish builtin -- every function expecting stock history
semantics (search, --max, merge, ...) would otherwise silently break.
hist.fish, which relied on the shadow's timestamp formatting, now
requests it explicitly via builtin history --show-time.

Add a CLASSIFICATION doc-header label so a function can declare its
interaction with C1-shadowed commands (uses-shadow/bypasses-shadow)
and general hazards (destructive, network, blocking-prompt) for
anyone deciding to disable an opinionated category or call the
function from automation. Wired into the manual/site build pipeline
(manualtools.py, build-manual.py) and the C1 shadow doc gets a new
"For function authors" bypass-mechanism reference table
(command/builtin/__original_help, and which shadows have no real
bypass target at all).

functions/hist.fish

@@ -34,7 +34,7 @@ function hist --description 'Search fish history and put it in the prompt'
         return 1
     end
 
-    set -l selected (history | fzf --reverse --height 40% --with-nth 3..)
+    set -l selected (builtin history --show-time='%F %T ' | fzf --reverse --height 40% --with-nth 3..)
 
     if test -n "$selected"
         # Strip the timestamp for the final output