fix(cli): multi-PRG build adds every input dir to the include path

Each PRG file's preprocessor instance was set up with only its OWN
directory on the include search path (`filepath.Dir(prgFile)`).
That worked for self-contained files but broke any multi-file
build where one PRG `#include`s a header that lives next to a
SIBLING PRG — the other file's directory wasn't on the path, so
the include silently failed and PP just skipped it ("// #include
\"FiveSqlDef.ch\" — not found (skipped)").

This was the root cause behind test_sql_standards's mass-failure
pattern. The test does

   #include "FiveSqlDef.ch"
   ...
   Assert( ..., h["columns"][1][1][1] == ND_FN .AND. ... )

`FiveSqlDef.ch` lives in `_FiveSql2/src/` (next to TSqlExecutor.prg
and friends), but the test source sits in `_FiveSql2/test/`.
Building with `./five build _FiveSql2/test/test_sql_standards.prg
_FiveSql2/src/*.prg` should resolve the header from a sibling
input file's directory — but only the test's own dir was searched,
so ND_FN / ND_LIT / ND_BIN / ND_UNI all stayed undefined and the
identifiers fell through to runtime memvar lookup, returning NIL.
Every assertion that compared against the constants therefore
silently failed (24 / 64 passing because non-constant assertions
still worked).

buildMultiPRGWithIncludes now seeds the user-include list with the
directory of every input PRG before handing off to buildMultiPRG.
A test under one directory can now resolve a `#include` that lives
next to a sibling source file in the same multi-file build.

Result: test_sql_standards goes from 24 / 64 to **64 / 64**. The
parser was already correct end-to-end — every SQL:2003-2023
construct it had been advertising actually worked; the test just
couldn't read the constants it was asserting against.

Wired test_sql_standards into the std.ch runner with a per-test
override so it picks up the FiveSql2 src files. Suite stands at
17/17.

Other gates green:
  go test ./...      : PASS
  FiveSql2 SQL:1999  : 43/43
  FiveSql2 standards : 64/64  (was 24/64)
  Harbour compat     : 56/56
  std.ch suite       : 17/17
  FRB suite          : 7/7

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cmd/five/main.go

@@ -324,6 +324,24 @@ func buildPRGWithIncludes(prgFile, output string, includes []string) {
 
 // buildMultiPRGWithIncludes is buildMultiPRG with -I support.
 func buildMultiPRGWithIncludes(prgFiles []string, output string, includes []string) {
+	// Multi-file builds bring along sibling PRGs whose own #include
+	// references a .ch file living next to them (e.g. FiveSqlDef.ch
+	// in _FiveSql2/src/). Each file's PP only adds its OWN dir by
+	// default, so a test under _FiveSql2/test/ couldn't find a .ch
+	// kept in _FiveSql2/src/. Promote every input file's dir into
+	// the shared user-include list so siblings can resolve each
+	// other's headers.
+	seen := map[string]bool{}
+	for _, dir := range includes {
+		seen[dir] = true
+	}
+	for _, f := range prgFiles {
+		dir := filepath.Dir(f)
+		if dir != "" && !seen[dir] {
+			seen[dir] = true
+			includes = append(includes, dir)
+		}
+	}
 	userIncludeDirs = includes
 	buildMultiPRG(prgFiles, output)
 }

tests/std_ch/run.sh

@@ -32,6 +32,7 @@ TESTS=(
    test_block_comma
    test_compound_lhs
    test_join_hash
+   test_sql_standards
 )
 
 work="$(mktemp -d)"
@@ -41,8 +42,17 @@ pass=0
 fail=0
 for name in "${TESTS[@]}"; do
    src="$ROOT/tests/std_ch/${name}.prg"
+   # test_sql_standards lives in our suite but its `#include
+   # "FiveSqlDef.ch"` resolves only when the FiveSql2 src files
+   # are part of the same build (they sit alongside the .ch).
+   # Other tests build standalone.
+   extras=()
+   if [ "$name" = "test_sql_standards" ]; then
+      src="$ROOT/_FiveSql2/test/test_sql_standards.prg"
+      extras=( $ROOT/_FiveSql2/src/*.prg )
+   fi
    bin="$work/${name}"
-   if ! "$FIVE" build "$src" -o "$bin" >/dev/null 2>"$work/${name}.err"; then
+   if ! "$FIVE" build "$src" "${extras[@]}" -o "$bin" >/dev/null 2>"$work/${name}.err"; then
       echo "FAIL build  $name"
       cat "$work/${name}.err" | sed 's/^/   /'
       fail=$((fail+1))