feat(KB-619): add multi-project CLI support

- Add project-resolver module with CentralCore integration for project resolution
- Add project subcommands: list, add, remove, info with proper CLI integration
- Add --project flag support across all task and settings commands
- Refactor getStore to use project resolution with options pattern
- Update bin.ts command routing to extract and propagate project context
- Add project context propagation via FN_PROJECT environment variable

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

@@ -0,0 +1,17 @@
+---
+"@gsxdsm/fusion": minor
+---
+
+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
+
+All task and settings commands now support `--project <name>` flag:
+- `fn task list --project myapp`
+- `fn settings --project myapp`
+
+Projects are auto-detected from cwd by walking up to find `.kb/`.