dissolve app/ into repo root (D-056)

Single Flutter package at the repo root. All code, tests, assets,
and platform directories moved from app/ to root. Package renamed
from clide_app to clide — all imports rewritten. Merged pubspec
combines core (ffi) and app (flutter, yaml, xterm) dependencies.
Makefile simplified: no APP_PRESENT conditionals, no cd, no daemon
lifecycle. 317 tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

assets/queries/diff.scm

@@ -0,0 +1,49 @@
+(comment) @comment @spell
+
+[
+  (addition)
+  (new_file)
+] @diff.plus
+
+[
+  (deletion)
+  (old_file)
+] @diff.minus
+
+(commit) @constant
+
+(location) @attribute
+
+(command
+  "diff" @function
+  (argument) @variable.parameter)
+
+(filename) @string.special.path
+
+(mode) @number
+
+([
+  ".."
+  "+"
+  "++"
+  "+++"
+  "++++"
+  "-"
+  "--"
+  "---"
+  "----"
+] @punctuation.special
+  (#set! priority 95))
+
+[
+  (binary_change)
+  (similarity)
+  (file_change)
+] @label
+
+(index
+  "index" @keyword)
+
+(similarity
+  (score) @number
+  "%" @number)