Add opt-in analyze support for extensionless/unknown file types

[Copilot]

Bug Fix

DevSkim analyze skipped files with unknown language classification, which prevented rules (including applies_to_file_regex) from evaluating extensionless targets like passwd. This change adds an explicit CLI opt-in to analyze unknown file types while preserving current default behavior.

• What was the bug?

  • Directory scans used *.*, excluding extensionless files from discovery.
  • Even when discovered, unknown-language files were unconditionally skipped before rule evaluation.

• How did you fix it?

  • New analyze flag (opt-in):
    • Added --analyze-unknown-file-types to BaseAnalyzeCommandOptions (default: false).
  • Extensionless file discovery:
    • Updated directory enumeration in AnalyzeCommand from *.* to * so files like passwd are included.
  • Unknown-language handling:
    • Kept existing default skip behavior.
    • When the new flag is set, unknown-language files are analyzed instead of skipped.
    • Output language is emitted as "unknown" for those files.

• Implementation details

  • Added focused analyzer coverage for an extensionless passwd file with applies_to_file_regex, asserting:
    • flag off ⇒ no findings
    • flag on ⇒ finding is produced

devskim analyze \
  --source-code /path/to/repo \
  --rules /path/to/passwd-rule.json \
  --analyze-unknown-file-types