fix: relieve code overflow that crashed string operations (#145)

## Problem

The resident (non-paged) code section had overflowed past `$C000` into
kernel-reserved I/O space by `$95` bytes — the standing `BROKEN BUILD`
assembler warning. This stranded `StringTempWrite` across the `$C000`
boundary (its body ran into `$C001+`, which the F256 maps to I/O
registers, not code). Since `StringTempWrite` is called whenever a
**temporary string** is built — string concatenation, `STR$`, `CHR$`,
substrings — any such operation executed I/O space as code and crashed
the machine.

Programs relying on string concatenation crashed. `ashanghai.bas` died
on its first concat (`"ashanghai/"+name$+".pal"`) during asset loading.

## Fix

Move the boot-only `DisplayBannerText` routine (and its print macros)
out of resident code into a slot 3 kernel module, called once at boot
via the generated banking thunk. The banner's string/build data stays
resident and is read from the module (resident code stays visible from
slot 3). This frees ~230 bytes of resident code.

Result: the `$C000` overflow is gone, and `StringTempWrite` (now at
`$befc`) sits safely below the boundary.

## Verification (MAME)

- Build shows **no** `$C000` overflow warning.
- Boot banner renders correctly (machine name, info, kernel, build
version/timestamp).
- `a$="x"+"y"` prints `xy`; `STR$`, `CHR$`, `LEFT$`, `MID$`, `RIGHT$`
all work.
- `ashanghai.bas` loads all assets and reaches the game.

Note: this is a stopgap for the space pressure; the general fix is the
paging rework.

Signed-off-by: Matthias Brukner <mbrukner@gmail.com>

Author: mbrukner

source/common/aa.system/00start.asm

@@ -106,156 +106,8 @@ Start:	ldx 	#$FF 						; stack reset
 		jmp 	WarmStart
 		.endif
 
-;;
-; Print hardware, ROM & build info at designated banner positions
-;;
-DisplayBannerText:
-		.print_machine_name
-		.print_machine_info
-		.print_kernel_info
-		.print_build_version
-		.print_build_timestamp
-
-		; position cursor below the banner
-		.set_line #Banner.Height-1
-		.print_char #13
-
-		rts
-
-print_char .macro
-		lda 	\1
-		jsr 	EXTPrintCharacter
-		.endm
-
-print_hex .macro
-		lda 	\1
-		jsr 	PrintHex
-		.endm
-
-set_color .macro
-		print_char 	\1+128
-		.endm
-
-set_column .macro
-		lda 	\1
-		sta		EXTColumn
-		.endm
-
-set_line .macro
-		lda 	\1
-		sta 	EXTRow
-		jsr 	EXTSetCurrentLine
-		.endm
-
-is_jr	.macro
-		stz 	$0001
-		lda 	$D6A7
-		and 	#$10
-		.endm
-
-print_machine_name .macro
-		.set_line   #Banner.Machine_Name_Line
-		.set_column #Banner.Machine_Name_Column
-		.set_color  #Banner.Machine_Name_Colors[0]
-		stz 	$0001
-		lda 	$D6A7
-		and 	#$32
-		cmp     #$10
-		beq 	_wld
-		cmp     #$22
-		beq 	_wld
-		lda 	#<Machine_Name_Prefix.FNX
-        ldx 	#>Machine_Name_Prefix.FNX
-        bra     +
-	_wld:
-		lda 	#<Machine_Name_Prefix.WLD
-        ldx 	#>Machine_Name_Prefix.WLD
-    +   jsr 	PrintStringXA
-
-		.set_color  #Banner.Machine_Name_Colors[1]
-		stz 	$0001
-		lda 	$D6A7
-		bit 	#$10
-		beq 	_jr_or_jr2
-		bit 	#$02
-		beq 	_k2
-		lda 	#<Machine_Name.K
-        ldx 	#>Machine_Name.K
-        bra     +
-    _k2:
-        lda 	#<Machine_Name.K2
-        ldx 	#>Machine_Name.K2
-        bra     +
-    _jr_or_jr2:
-        bit 	#$20
-        beq 	_jr
-		lda 	#<Machine_Name.Jr2
-        ldx 	#>Machine_Name.Jr2
-        bra     +
-    _jr:
-	    lda 	#<Machine_Name.Jr
-        ldx 	#>Machine_Name.Jr
-    +   jsr 	PrintStringXA
-
-		.endm
-
-print_machine_info .macro
-		.set_color  #Banner.Machine_Info_Color
-		.set_line   #Banner.Machine_Info_Line
-		.set_column #Banner.Machine_Info_Column
-
-		stz 	$0001
-
-		.print_hex $D6AD
-        .print_hex $D6AC
-        .print_hex $D6AB
-        .print_hex $D6AA
-        .print_char #' '
-        .print_char $D6A8
-        .print_char $D6A9
-
-        .print_char #' '
-        ;
-        ; print core version (1x vs 2x)
-        ;
-        lda		#'1'						; default to '1'
-        bit 	$D6A7 						; test the 7th bit of machine ID
-        bpl 	+
-        lda		#'2'
-    +   jsr 	EXTPrintCharacter
-        .print_char #'x'
-
-        .endm
-
-print_kernel_info .macro
-		.set_color  #Banner.Kernel_Info_Color
-		.set_line   #Banner.Kernel_Info_Line
-		.set_column #Banner.Kernel_Info_Column
-
-        lda 	#$08
-		ldx 	#$E0
-		jsr 	PrintStringXA
-		.endm
-
-print_build_version .macro
-		.set_color  #Banner.Build_Version_Color
-		.set_line   #Banner.Build_Version_Line
-		.set_column #Banner.Build_Version_Column
-
-        lda 	#<Build_Version
-		ldx 	#>Build_Version
-		jsr 	PrintStringXA
-		.endm
-
-print_build_timestamp .macro
-		.set_color  #Banner.Build_Timestamp_Color
-		.set_line   #Banner.Build_Timestamp_Line
-		.set_column #Banner.Build_Timestamp_Column
-
-        lda 	#<Build_Timestamp
-		ldx 	#>Build_Timestamp
-		jsr 	PrintStringXA
-		.endm
+; Machine name, build version and timestamp data. Kept resident (read by the
+; DisplayBannerText code, now in the slot 3 kernel module bannerinfo.asm).
 
 Machine_Name_Prefix .namespace
 FNX:    .text 	"FOENIX ", 0

source/modules/kernel/startup/bannerinfo.asm

@@ -0,0 +1,164 @@
+; ************************************************************************************************
+; ************************************************************************************************
+;
+;		Name:		bannerinfo.asm
+;		Purpose:	Print hardware/ROM/build info banner (slot 3 module)
+;		Created:	10th July 2026
+;		Author:		Matthias Brukner (mbrukner@gmail.com)
+;
+;		Moved out of the resident code section (00start.asm) to relieve the
+;		non-paged code overflow past $C000. Called once at boot via the
+;		generated slot-3 thunk. String/build data stays resident in
+;		00start.asm and is read from here (resident code is visible).
+;
+; ************************************************************************************************
+; ************************************************************************************************
+
+		.section code
+
+;;
+; Print hardware, ROM & build info at designated banner positions
+;;
+Export_DisplayBannerText:
+		.print_machine_name
+		.print_machine_info
+		.print_kernel_info
+		.print_build_version
+		.print_build_timestamp
+
+		; position cursor below the banner
+		.set_line #Banner.Height-1
+		.print_char #13
+
+		rts
+
+print_char .macro
+		lda 	\1
+		jsr 	EXTPrintCharacter
+		.endm
+
+print_hex .macro
+		lda 	\1
+		jsr 	PrintHex
+		.endm
+
+set_color .macro
+		print_char 	\1+128
+		.endm
+
+set_column .macro
+		lda 	\1
+		sta		EXTColumn
+		.endm
+
+set_line .macro
+		lda 	\1
+		sta 	EXTRow
+		jsr 	EXTSetCurrentLine
+		.endm
+
+print_machine_name .macro
+		.set_line   #Banner.Machine_Name_Line
+		.set_column #Banner.Machine_Name_Column
+		.set_color  #Banner.Machine_Name_Colors[0]
+		stz 	$0001
+		lda 	$D6A7
+		and 	#$32
+		cmp     #$10
+		beq 	_wld
+		cmp     #$22
+		beq 	_wld
+		lda 	#<Machine_Name_Prefix.FNX
+        ldx 	#>Machine_Name_Prefix.FNX
+        bra     +
+	_wld:
+		lda 	#<Machine_Name_Prefix.WLD
+        ldx 	#>Machine_Name_Prefix.WLD
+    +   jsr 	PrintStringXA
+
+		.set_color  #Banner.Machine_Name_Colors[1]
+		stz 	$0001
+		lda 	$D6A7
+		bit 	#$10
+		beq 	_jr_or_jr2
+		bit 	#$02
+		beq 	_k2
+		lda 	#<Machine_Name.K
+        ldx 	#>Machine_Name.K
+        bra     +
+    _k2:
+        lda 	#<Machine_Name.K2
+        ldx 	#>Machine_Name.K2
+        bra     +
+    _jr_or_jr2:
+        bit 	#$20
+        beq 	_jr
+		lda 	#<Machine_Name.Jr2
+        ldx 	#>Machine_Name.Jr2
+        bra     +
+    _jr:
+	    lda 	#<Machine_Name.Jr
+        ldx 	#>Machine_Name.Jr
+    +   jsr 	PrintStringXA
+
+		.endm
+
+print_machine_info .macro
+		.set_color  #Banner.Machine_Info_Color
+		.set_line   #Banner.Machine_Info_Line
+		.set_column #Banner.Machine_Info_Column
+
+		stz 	$0001
+
+		.print_hex $D6AD
+        .print_hex $D6AC
+        .print_hex $D6AB
+        .print_hex $D6AA
+        .print_char #' '
+        .print_char $D6A8
+        .print_char $D6A9
+
+        .print_char #' '
+        ;
+        ; print core version (1x vs 2x)
+        ;
+        lda		#'1'						; default to '1'
+        bit 	$D6A7 						; test the 7th bit of machine ID
+        bpl 	+
+        lda		#'2'
+    +   jsr 	EXTPrintCharacter
+        .print_char #'x'
+
+        .endm
+
+print_kernel_info .macro
+		.set_color  #Banner.Kernel_Info_Color
+		.set_line   #Banner.Kernel_Info_Line
+		.set_column #Banner.Kernel_Info_Column
+
+        lda 	#$08
+		ldx 	#$E0
+		jsr 	PrintStringXA
+		.endm
+
+print_build_version .macro
+		.set_color  #Banner.Build_Version_Color
+		.set_line   #Banner.Build_Version_Line
+		.set_column #Banner.Build_Version_Column
+
+        lda 	#<Build_Version
+		ldx 	#>Build_Version
+		jsr 	PrintStringXA
+		.endm
+
+print_build_timestamp .macro
+		.set_color  #Banner.Build_Timestamp_Color
+		.set_line   #Banner.Build_Timestamp_Line
+		.set_column #Banner.Build_Timestamp_Column
+
+        lda 	#<Build_Timestamp
+		ldx 	#>Build_Timestamp
+		jsr 	PrintStringXA
+		.endm
+
+		.send code