feat: support multiple authentication profiles for the same workspace

[rafael-yure]

Motivation

SlackCLI currently stores authenticated credentials in workspaces.json keyed by Slack team_id:

{
  "workspaces": {
    "T123": {
      "workspace_id": "T123",
      "workspace_name": "example",
      "auth_type": "standard"
    }
  },
  "default_workspace": "T123"
}

This means authenticating a second identity or authentication mode for the same Slack workspace silently replaces the first one.

A common automation setup needs both:

• a browser-authenticated user profile for workspace search, drafts, and user-authored messages;
• a stable bot-token profile for unattended jobs and bot-authored messages.

SlackCLI supports both authentication modes individually, but cannot retain them simultaneously when they belong to the same Slack team.

Proposal

Allow authentication records to have unique, user-selected profile names:

slackcli auth login \
  --token=xoxb-... \
  --workspace-name=example \
  --profile=automation-bot

slackcli auth login-browser \
  --xoxd=xoxd-... \
  --xoxc=xoxc-... \
  --workspace-url=https://example.slack.com \
  --profile=rafael

Existing commands can continue using --workspace, extended to accept a profile name:

slackcli search messages "after:2026-07-01" --workspace=rafael --json
slackcli messages send --recipient-id=C123 --message="Done" --workspace=automation-bot

auth list, auth set-default, and auth remove should operate on and display the stored profile keys.

Compatibility

• Existing workspaces.json files should continue working without manual migration.
• Existing workspace ID and workspace name selectors should keep working when they resolve to exactly one profile.
• If a workspace ID or name matches multiple profiles, SlackCLI should return a clear ambiguity error asking for a profile name instead of picking one silently.
• Login without --profile should preserve today's behavior for users with one identity, while avoiding silent replacement when another profile already exists for that team.

Suggested implementation

• Add an optional profile identifier to stored workspace configurations.
• Store credential records by profile key rather than solely by team_id.
• Extend workspace resolution to prefer exact profile keys/names, then fall back to an unambiguous workspace ID or name.
• Normalize legacy records on load or support them transparently through the resolver.
• Add focused tests for legacy config compatibility, two profiles in one team, ambiguous selection, defaults, and removal.

This keeps the Slack client and dual-auth implementation unchanged; the enhancement is isolated to authentication commands, configuration persistence, selection, and documentation.

Fork

I'm working on this on a personal fork; let me know if it's okay to submit a PR with the implementation.