CLI commands crash with unhandled ParseError on malformed input

[dithesh12]

Summary

CLI commands (parse and validate) crash with an unhandled ParseError when processing malformed or truncated input files. Instead of handling the error gracefully, the application terminates with a full Python traceback.

This contradicts the framework’s goal of handling malformed and truncated telemetry streams.

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Reproduction

1. Copy a valid sample file:
   copy samples\valid_telemetry.sgf broken.sgf

2. Open broken.sgf and delete part of the second frame (truncate the file)

3. Run:
   python -m sigflow parse broken.sgf

4. Observe the CLI crashes with a traceback

5. Repeat:
   python -m sigflow validate broken.sgf

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Expected Behavior

The CLI should handle malformed or truncated input gracefully and display a structured error message (e.g., "truncated input at offset X") instead of crashing with a full traceback.

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Actual Behavior

The CLI crashes with an unhandled exception:

sigflow.core.exceptions.ParseError: truncated input

A full Python traceback is displayed instead of a user-friendly error message.

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Environment

• Python version: 3.13.2
• sigflow version or commit: 0.1.0 (local install from repository)
• Operating system: Windows 10

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Additional Context

The error originates from sigflow/parsers/base.py where ParseError is raised when truncated input is detected.

However, CLI commands in sigflow/cli/commands.py (specifically parse_command and validate_command) do not catch this exception, allowing it to propagate and terminate the program.

This makes the CLI tools less robust for real-world telemetry pipelines where malformed inputs are expected.

[jmestwa-coder]

@dithesh12
This does look like a CLI error-handling issue rather than a parser issue itself. The parser raising ParseError for truncated input is expected, but the CLI probably should not expose a full traceback for malformed user input.

Please open a PR with a minimal fix scoped to the CLI layer only (for example, handling ParseError inside parse_command and validate_command and returning a structured user-facing error message with a non-zero exit code).

Please avoid changing parser semantics or adding recovery behavior in the parser itself.