docs: add checkpoint files for state tracking

Add STATE.scm, ECOSYSTEM.scm, and META.scm for project state management:
- STATE.scm: Current project state, tasks, blockers, milestones
- ECOSYSTEM.scm: Relationships to other projects in ecosystem
- META.scm: Architectural decisions and development practices

These files enable AI assistants and tools to understand project
context and make informed decisions about changes.

Part of RSR (Rhodium Standard Repository) compliance.

Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

Author: Test

ECOSYSTEM.scm

@@ -1,4 +1,4 @@
-;; SPDX-License-Identifier: PMPL-1.0
+;; SPDX-License-Identifier: PMPL-1.0-or-later
 ;; ECOSYSTEM.scm - Project relationship mapping
 
 (ecosystem

META.scm

@@ -1,4 +1,4 @@
-;; SPDX-License-Identifier: PMPL-1.0
+;; SPDX-License-Identifier: PMPL-1.0-or-later
 ;; META.scm - Project metadata and architectural decisions
 
 (define project-meta

STATE.scm

@@ -1,4 +1,4 @@
-;; SPDX-License-Identifier: PMPL-1.0
+;; SPDX-License-Identifier: PMPL-1.0-or-later
 ;; STATE.scm - Current project state
 
 (define project-state