Support multiple base catalogs in builder

[rsnodgrass]

Summary

The Build() function and CLI --catalog flag currently accept a single CatalogData as the base. Users with multiple catalogs (hand-crafted + team-shared + previous build) must manually merge them before building.

Proposed Changes

• Library: Add MergeCatalogs(catalogs ...CatalogData) CatalogData that deduplicates by pattern (lower-cased), keeping the entry with highest confidence when duplicates exist. Last-writer-wins for version string.
• CLI: Change --catalog to accept multiple values (cobra StringSliceVar), load each, merge, then pass to Build().
• Build() signature stays the same — callers that want multi-catalog support call MergeCatalogs() first. No breaking change.

Example Usage

frictionax catalog build \
  --catalog hand-crafted.json \
  --catalog team-shared.json \
  --server https://api.sageox.ai/v1/agentx/myapp/friction/patterns \
  --output catalog.json

Why

AgentX users will have hand-crafted catalogs they want to preserve when building from SageOx telemetry patterns. Forcing manual pre-merge adds friction to the catalog building workflow.

Current Behavior

• --catalog accepts one file (default: default_catalog.json)
• Build() takes one CatalogData as existing
• Deduplication works against that single base
• Hand-crafted entries are preserved in the output

Merge Strategy

When the same pattern (case-insensitive) appears in multiple catalogs:

1. Keep the entry with highest confidence
2. If equal, prefer the entry with a non-empty target
3. Tokens: deduplicate by pattern + kind key