Report invalid --format-options as a CLI error, not a traceback

[seven7763]

Summary

Fixes #1938.

An invalid --format-options value crashed with an unhandled argparse.ArgumentTypeError traceback:

$ http --offline --format-options=json.indent:x pie.dev/get
argparse.ArgumentTypeError: invalid value 'x' in 'json.indent:x' (expected int got str)

_process_format_options() calls parse_format_options() manually after parsing, so the ArgumentTypeError raised for bad input is never converted into a normal CLI error. This catches it there and routes it through self.error(), which is the same pattern the parser already uses for other invalid-flag combinations.

$ http --offline --format-options=json.indent:x example.org

error:
    invalid value 'x' in 'json.indent:x' (expected int got str)

Changes

• httpie/cli/argparser.py: wrap the parse_format_options() loop in _process_format_options() with try/except argparse.ArgumentTypeError → self.error(str(ex))
• tests/test_output.py: 3 regression tests (bad type / unknown key / bare section), asserting a clean error: message, ExitStatus.ERROR, and no traceback

Validation

• Reproduced all three variants from the issue on main before the fix (all traceback)
• After the fix: all three produce the standard CLI error and exit 1
• python -m pytest tests/test_output.py -q — 123 passed; the one failure (TestQuietFlag::test_double_quiet_on_error) also fails on unmodified main in this environment and is untouched by this change

Notes

No message wording changed — the same messages from parse_format_options() are surfaced, just without the traceback.

[seven7763]

Heads-up on CI: the failures here (encoding/charset tests + coverage) are repo-wide — PR #1944 shows the same 37 failing checks with unrelated changes. Locally pytest tests/test_output.py passes (123 passed; the one failure, TestQuietFlag::test_double_quiet_on_error, also fails on unmodified main locally).