feat: comprehensive registry improvements

Community docs:
- CODE_OF_CONDUCT.md (Contributor Covenant v2.1)
- SECURITY.md (vulnerability reporting policy)
- CHANGELOG.md (initial release notes)
- CODEOWNERS (per-type review ownership)

GitHub config:
- Issue templates: bug-report, pricing-correction, documentation
- FUNDING.yml (GitHub Sponsors)

Validation enhancements:
- Cross-reference check: hand [[requires]] → integration existence
- Routing alias collisions as warnings (errors with --strict)
- --strict flag to promote warnings to errors
- --type filter to validate single content type
- CI: add taplo format check and lychee link check jobs

Developer experience:
- Makefile with validate, fmt, and scaffold targets
- Scaffold templates for all 5 content types
- .pre-commit-config.yaml (trailing whitespace, TOML check, validate)
- docs/content-guide.md (naming, descriptions, prompts, decision guide)

Content quality:
- schema.toml: add last_verified field for model pricing
- CONTRIBUTING.md: add pricing verification guide with source links

templates/agent.toml

@@ -0,0 +1,32 @@
+name = "{{NAME}}"
+version = "0.1.0"
+description = "TODO: One-sentence description of what this agent does."
+author = "TODO"
+module = "builtin:chat"
+
+[metadata.routing]
+aliases = ["TODO: exact match phrases"]
+weak_aliases = ["TODO: partial match keywords"]
+
+[model]
+provider = "default"
+model = "default"
+max_tokens = 4096
+temperature = 0.7
+system_prompt = """TODO: Write a clear system prompt that defines:
+- Who the agent is and its role
+- What it should and should not do
+- How it should format responses
+- Any domain-specific instructions
+
+Keep it focused and under 500 words."""
+
+[resources]
+max_llm_tokens_per_hour = 100000
+
+[capabilities]
+tools = ["web_search", "web_fetch", "memory_store", "memory_recall"]
+network = ["*"]
+memory_read = ["*"]
+memory_write = ["self.*"]
+agent_spawn = false