feat: add specification for external provider injection (Level 1)

Add comprehensive specification documents for deploy-time modularity
feature that enables external provider integration without rebuilding
distribution images.

Specification documents:
- spec.md: Core requirements and user stories (32 functional requirements)
- plan.md: Implementation approach with two-phase init container architecture
- tasks.md: Breakdown of 110 tasks across 7 implementation phases
- integration-points.md: Detailed integration with existing codebase (10 points)
- extra-providers-schema.md: Forward-compatible schema for future LlamaStack support
- pr-strategy.md: 8-PR breakdown strategy to avoid overwhelming reviewers
- implementation-notes.md: Technical brainstorming and design decisions
- lls-preflight-spec.md: Provider validation specification
- constitution.md: Project-wide principles and standards

Key architectural decisions:
- Two-phase init containers (Install → Merge) for simplicity
- extra-providers.yaml schema enables forward compatibility
- Merge tool binary in operator image supports Phase 2 migration
- CRD-ordered init containers for deterministic behavior
- Proper markdown formatting for GitHub rendering

Signed-off-by: Roland Huß <rhuss@redhat.com>

Author: rhuss

.gitignore

@@ -34,3 +34,7 @@ catalog-item
 config/manifests/bases/llama-stack-k8s-operator.clusterserviceversion.yaml
 
 .DS_Store
+
+# SDD and Claude Code directories
+.claude
+.specify