Add beachball config get and config list commands

[Copilot]

Summary

Adds beachball config get <name> and beachball config list commands for inspecting the effective beachball configuration.

config get <name>

Gets the value of a specific config setting, including any per-package or per-group overrides. Supports --package to query the effective value for specific packages (accounting for group membership).

$ beachball config get branch
"origin/main"

$ beachball config get disallowedChangeTypes
Main value: null

Group overrides:
  my-group:
    disallowedChangeTypes: ["major"]
    packageNames: ["pkg-a", "pkg-b"]

$ beachball config get disallowedChangeTypes --package pkg-a
pkg-a: ["major"]

config list

Lists all config settings (including defaults), plus any group and per-package overrides, using YAML-like formatting.

$ beachball config list
Main options (including defaults):
  access: "restricted"
  branch: "origin/main"
  bump: true
  ...

Group overrides:
  my-group:
    packageNames: ["pkg-a", "pkg-b"]
    disallowedChangeTypes: ["major"]

Other changes

• src/logging/formatValue.ts — New YAML-like value formatter with width-aware single-line/multi-line output, used by both commands
• src/options/getCliOptions.ts — Added _extraPositionalArgs support for subcommand parsing
• src/help.ts and docs/cli/config.md — Help text and doc site page for both commands
• .claude/skills/beachball-change-file/SKILL.md — Updated to use beachball config get instead of manually reading config files

[ecraig12345]

@copilot address the comments below and add a change file

[Copilot]

@copilot address the comments below and add a change file

Addressed both review comments in 32cd00f and added the change file in 1843a25.