Pin pointer alignment, check make indent in CI, and reformat

`DerivePointerAlignment` (inherited from the Google base style) made the
placement of `*` and `&` depend on whichever way the surrounding file
already leaned, so reformatting could silently move them. Set
`PointerAlignment: Right` and turn derivation off so the rule is the same
everywhere.

Add an `indent` CI job in the same shape as the `docs` one: reformat, then
fail on any diff. It pins clang-format 18.1.8, since different versions
format the same input differently and would otherwise fail the check
spuriously.

Reformat the sources so the new job passes. Most of the diff is drift that
accumulated while nothing was checking: trailing whitespace, spaces where
tabs belong, hand-aligned continuation lines, and casts missing the space
that `SpaceAfterCStyleCast` asks for.

Also drop the exclusion of flatgeobuf.cpp, which was the one hand-written
source the formatter never saw, and reformat it too. Only whitespace,
brace placement, and single-statement `if` bodies change; the code itself
is untouched.

serial.cpp

@@ -676,7 +676,7 @@ int serialize_feature(struct serialization_state *sst, serial_feature &sf, std::
 	} else if (extent < 0) {
 		sf.extent = LLONG_MIN;
 	} else {
-		sf.extent = LLONG_MAX;  // also the NaN case
+		sf.extent = LLONG_MAX;	// also the NaN case
 	}
 
 	if (sst->want_dist && sf.t == VT_POLYGON) {