chore: the editor reads the selected preset's database, and the config states no history

clangd's database is the one CMake Tools copies from the selected preset,
as in libavr, rather than one chip's tree. .gitattributes drops two Studio
patterns nothing here matches, .clangd is ASCII, and the comments in it,
check.sh and .gitattributes state the reason without the account of how it
was found.

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

.clangd

@@ -1,13 +1,13 @@
 # Editor accommodations for the second frontend. No compilation database is
 # named here: this driver is made to be vendored, and this file travels with
-# it — a consumer's own database then covers these headers, at the consumer's
+# it - a consumer's own database then covers these headers, at the consumer's
 # chip. The checkout that is opened as a folder names its build tree in
 # .vscode/settings.json instead.
 CompileFlags:
   Add:
     # clang has no 24-bit integer and GCC's are keywords, not macros, so the
     # editor needs a stand-in for avr::uint24_t. The next width up is the only
-    # one available — clang rejects _BitInt(24) on this target.
+    # one available - clang rejects _BitInt(24) on this target.
     - -D__uint24=unsigned long
     - -D__int24=long
     # clangd forwards the driver's system includes but not its own header
@@ -16,7 +16,7 @@ CompileFlags:
     - -D__STDC_LIMIT_MACROS
     - -D__STDC_CONSTANT_MACROS
     # isr::emit spells a vector number into [[gnu::signal(N)]], which clang
-    # rejects rather than ignores — enough of them in one TU to reach the
+    # rejects rather than ignores - enough of them in one TU to reach the
     # default limit of 19 inside the headers and truncate the parse.
     - -ferror-limit=0
   Remove: