feat(KB-619): enhance project commands with JSON output and task counts

- Add --json flag to 'kb project list' for machine-readable output
- Add --json flag to 'kb project show' for structured data
- Show task counts per column in project details
- Update CLI help text for better documentation
- Add changeset for multi-project CLI commands feature
- Add comprehensive tests for project commands

.changeset/add-cli-multi-project-commands.md

@@ -5,13 +5,16 @@
 Add CLI multi-project commands and --project flag support.
 
 New commands:
-- `fn project list [--json]` — List all registered projects
-- `fn project add [dir] [--name <name>] [--isolation <mode>]` — Register a project
-- `fn project remove <name> [--force]` — Unregister a project
-- `fn project info [name]` — Show project details
+- `kb project list [--json]` — List all registered projects with task counts and health
+- `kb project add [name] [path] [--isolation <mode>] [--interactive]` — Register a project
+- `kb project remove <name> [--force]` — Unregister a project
+- `kb project show <name>` — Show project details with health and task counts
+- `kb project info [name]` — Alias for show command
+- `kb project set-default <name>` — Set default project
+- `kb project detect` — Detect project from current directory
 
 All task and settings commands now support `--project <name>` flag:
-- `fn task list --project myapp`
-- `fn settings --project myapp`
+- `kb task list --project myapp`
+- `kb settings --project myapp`
 
 Projects are auto-detected from cwd by walking up to find `.kb/`.