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

test/hyphenation_eval/resources/generate_hyphenation_test_data.py

@@ -16,7 +16,6 @@ Requirements:
 import argparse
 import re
 from collections import Counter
-import pyphen
 from pathlib import Path
 import zipfile
 
@@ -75,6 +74,8 @@ def generate_hyphenation_data(
         min_prefix: Minimum characters allowed before the first hyphen (default: 2)
         min_suffix: Minimum characters allowed after the last hyphen (default: 2)
     """
+    import pyphen
+
     print(f"Reading from: {input_file}")
 
     # Read the input file