fix: make script help paths lightweight (#1937)

## Summary

Consolidate the script help/startup fixes so standalone helper commands
can show usage without requiring runtime-only dependencies or generating
files.

## Details

Several helper scripts imported optional packages, evaluated newer
annotations, or started generation before users could inspect CLI usage.
On a fresh checkout, this made common help paths fail on missing
packages such as `cairosvg`, `Pillow`, `freetype-py`, `fontTools`,
`pyphen`, `pyserial`, or on Python 3.9 annotation evaluation. A few
generators also treated `--help` as a normal output argument and wrote
files instead of printing usage.

This change keeps runtime dependencies on the code paths that need them,
handles lightweight help/list commands first, and adds explicit `--help`
handling for generator scripts that previously started work.

## Validation

- `python3 <script> --help` across tracked Python scripts, excluding
`scripts/patch_jpegdec.py` because it is a PlatformIO pre-build hook
rather than a standalone CLI
- `python3 scripts/convert_icon.py` still exits with usage for missing
required arguments
- `python3 lib/EpdFont/scripts/fontconvert_sdcard.py --list-presets`
- `python3 -m py_compile` for the changed scripts

lib/EpdFont/scripts/fontconvert.py

@@ -1,12 +1,10 @@
 #!python3
-import freetype
 import zlib
 import sys
 import re
 import math
 import argparse
 from collections import namedtuple
-from fontTools.ttLib import TTFont
 
 # Force UTF-8 stdout so that `python fontconvert.py … > foo.h` on Windows
 # (default cp1252) doesn't emit UTF-16 LE / replacement chars in the generated
@@ -27,6 +25,9 @@ parser.add_argument("--force-autohint", dest="force_autohint", action="store_tru
 parser.add_argument("--pnum", dest="pnum", action="store_true", help="Use proportional numerals (pnum OpenType feature) instead of default tabular figures. Reduces visual gaps between digits in running prose.")
 args = parser.parse_args()
 
+import freetype
+from fontTools.ttLib import TTFont
+
 GlyphProps = namedtuple("GlyphProps", ["width", "height", "advance_x", "left", "top", "data_length", "data_offset", "code_point"])
 
 font_stack = [freetype.Face(f) for f in args.fontstack]

lib/EpdFont/scripts/fontconvert_sdcard.py

@@ -22,7 +22,8 @@ Usage:
 
 """
 
-import freetype
+from __future__ import annotations
+
 import struct
 import sys
 import os
@@ -31,8 +32,6 @@ import math
 import argparse
 from collections import namedtuple
 
-from fontTools.ttLib import TTFont
-
 from cpfont_version import CPFONT_VERSION
 
 # --- Unicode interval presets ---
@@ -252,6 +251,8 @@ def extract_kerning_fonttools(font_path, codepoints, ppem):
     codepoints.  Values are scaled from font design units to integer
     pixels at ppem.
     """
+    from fontTools.ttLib import TTFont
+
     font = TTFont(font_path)
     units_per_em = font['head'].unitsPerEm
     cmap = font.getBestCmap() or {}
@@ -402,6 +403,8 @@ def extract_ligatures_fonttools(font_path, codepoints):
     Returns list of (packed_pair, ligature_codepoint) for the given codepoints.
     Multi-character ligatures are decomposed into chained pairs.
     """
+    from fontTools.ttLib import TTFont
+
     font = TTFont(font_path)
     cmap = font.getBestCmap() or {}
 
@@ -514,6 +517,8 @@ def extract_ligatures_fonttools(font_path, codepoints):
 
 def rasterize_font_style(fontfile, size, intervals, style_id=0, force_autohint=False):
     """Rasterize all glyphs for one font style. Returns StyleRasterData."""
+    import freetype
+
     style_names = {0: "regular", 1: "bold", 2: "italic", 3: "bolditalic"}
     style_label = style_names.get(style_id, str(style_id))
 

lib/EpdFont/scripts/verify_compression.py

@@ -234,6 +234,9 @@ def main():
     if len(sys.argv) < 2:
         print(f"Usage: {sys.argv[0]} <font_headers_directory>", file=sys.stderr)
         sys.exit(1)
+    if sys.argv[1] in ("-h", "--help"):
+        print(f"Usage: {sys.argv[0]} <font_headers_directory>")
+        sys.exit(0)
 
     font_dir = sys.argv[1]
     if not os.path.isdir(font_dir):