add Plano agent skills framework and rule set (#797)

* feat: add initial documentation for Plano Agent Skills

* feat: readme with examples

* feat: add detailed skills documentation and examples for Plano

---------

Co-authored-by: Adil Hafeez <adil.hafeez@gmail.com>

skills/plano-config-fundamentals/SKILL.md

@@ -0,0 +1,34 @@
+---
+name: plano-config-fundamentals
+description: Validate and fix Plano config fundamentals. Use for config versioning, listener types, provider registration, secrets handling, and startup validation failures.
+license: Apache-2.0
+metadata:
+  author: katanemo
+  version: "1.0.0"
+---
+
+# Plano Configuration Fundamentals
+
+Use this skill for foundational `config.yaml` correctness.
+
+## When To Use
+
+- "Validate this Plano config"
+- "Fix startup config errors"
+- "Check listeners/providers/secrets"
+- "Why does `planoai up` fail schema validation?"
+
+## Apply These Rules
+
+- `config-version`
+- `config-listeners`
+- `config-providers`
+- `config-secrets`
+
+## Execution Checklist
+
+1. Ensure `version: v0.3.0` is present.
+2. Confirm listener type matches intended architecture.
+3. Verify provider names/interfaces and exactly one default provider.
+4. Replace hardcoded secrets with `$ENV_VAR` substitution.
+5. Return minimal patch and a `planoai up` verification plan.