feat: add auth credentials remove command

[yamagucci]

Summary

• Add gog auth credentials remove subcommand to remove stored OAuth client credentials
• Previously only set and list were available — there was no way to remove credentials via the CLI
• Also removes associated refresh tokens for all accounts authenticated under the deleted client
• Cleans up domain mappings (--domain) that reference the removed client

Usage

# Remove default client credentials (+ its tokens)
gog auth credentials remove

# Remove a named client
gog auth credentials remove work

# Remove all stored credentials
gog auth credentials remove all

# Preview what would be removed
gog auth credentials remove --dry-run

# Skip confirmation prompt
gog auth credentials remove --force

Confirmation prompt example

Proceed to remove OAuth credentials for client "work" and 2 associated token(s) (alice@co.com, bob@co.com)? [y/N]:

Implementation

• config.DeleteClientCredentialsFor(client) — removes the credentials JSON file
• AuthCredentialsRemoveCmd — CLI command following the same patterns as auth remove
  • Accepts optional positional [<client>] argument
  • Supports all to remove every stored credential
  • Falls back to --client flag or default when no arg is given
  • Finds and deletes all tokens stored under the target client
  • Cleans up domain mappings referencing the deleted client
  • Confirmation prompt shows affected accounts, --dry-run, --force, --json output

Test plan

• go build ./... passes
• go test ./internal/config/... ./internal/cmd/... passes
• gog auth credentials remove --help shows correct usage
• Manual test: set + add accounts + remove + list cycle

🤖 Generated with Claude Code

[steipete]

Landed in c73bb23 after a polish pass.

Changes added while landing:

• propagated credentials/config/keyring errors instead of swallowing them
• added dry-run JSON behavior for remove/remove-all
• removed associated tokens and domain mappings deterministically
• added regression coverage and README/spec/CHANGELOG entries

Verified locally with make fmt, make lint, make test, make build, and make ci.

Thanks again @yamagucci.