Feature: Support multiple Linear accounts via profiles

[jzillmann]

Problem

Currently the CLI stores a single token at ~/.config/linear/token. Users with access to multiple Linear workspaces (e.g., corporate + personal) must log out and back in to switch between them.

Current State

The codebase already has some infrastructure for this:

• WorkspaceConfig struct exists with per-workspace OAuth credentials
• GetLinearCredentials(workspace string) method exists but isn't wired to CLI
• Token storage in internal/token/storage.go is hardcoded to single path

Proposed Solution

Add profile-based multi-account support:

Token Storage:

~/.config/linear/tokens/
├── default.json
├── work.json
└── personal.json

Config:

default_profile: work
profiles:
  work:
    name: "Corporate"
    oauth: { client_id: ..., client_secret: ... }
  personal:
    name: "Personal"
    oauth: { client_id: ..., client_secret: ... }

Commands:

linear profile list          # List profiles
linear profile use <name>    # Set default
linear profile add <name>    # Add new profile
linear profile remove <name> # Remove profile

UX Decision Needed

1. Per-directory .linear-profile files - Auto-detect profile based on cwd (like .nvmrc)
2. Global default + switch - linear profile use <name> sets default, no flags needed
3. Both - Per-directory with global fallback

Files to Modify

• internal/token/storage.go - Profile-aware token paths
• internal/config/manager.go - Profile config types
• internal/cli/root.go - Profile flag/detection
• internal/cli/auth.go - Profile-aware auth
• internal/cli/profile.go (new) - Profile commands

Migration

Automatically migrate existing token to tokens/default.json on first run.