feat: add dotfile-based option defaults for CliApp (#191)

[Flamki]

Implements support for reading CLI option defaults from per-app dotfiles.

Fixes #191
/claim #191

What this adds

• Resolves .<app-name> files from:
  1. user home directory (lowest priority)
  2. parent directories from filesystem root down to cwd
  3. current working directory (highest file priority)
• Parses supported config lines:
  • --key=value
  • --key value
  • --flag
  • ignores empty lines and # comments
• Merges file options with CLI args so CLI always wins
• Prints applied config values and source files
• Keeps built-in command behavior stable (--help, --wizard, completion paths)

Implementation

• New config engine in zio.cli.config:
  • ConfigFileResolver
  • ConfigParser
  • ConfigMerger
  • ConfigDiagnostics
• Platform-specific resolvers:
  • JVM + Native implementations
  • JS no-op implementation
• CliApp.run integration point before command.parse
• Help + docs update for config-file behavior

Tests

Added:

• zio.cli.config.ConfigParserMergerSpec
• zio.cli.config.ConfigFileResolverSpec (JVM integration)

Validated locally:

• zioCliJVM/testOnly zio.cli.config.ConfigParserMergerSpec zio.cli.config.ConfigFileResolverSpec
• scalafmtCheckAll
• zioCliJS/compile
• zioCliNative/compile

Notes

• This PR intentionally avoids changing core option/command parser contracts.
• I can attach a short demo video in a follow-up comment if maintainers want it attached directly in PR discussion.

[CLAassistant]

All committers have signed the CLA.

[Flamki]

Updated demo video (fullscreen terminal, clean capture, no recorder UI):

https://github.com/Flamki/zio-cli/releases/download/demo-191-video/pr-558-demo-fullscreen-20260326-190242.mp4

This run shows:

• feature branch + commit summary
• key config-file implementation references
• target specs passing (ArgumentCollisionSpec, ConfigParserMergerSpec, ConfigFileResolverSpec)
• PR metadata (gh pr view 558)