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/rules/config-version.md

@@ -0,0 +1,44 @@
+---
+title: Always Specify a Supported Config Version
+impact: CRITICAL
+impactDescription: Plano rejects configs with missing or unsupported version fields — the version field gates all other validation
+tags: config, versioning, validation
+---
+
+## Always Specify a Supported Config Version
+
+Every Plano `config.yaml` must include a `version` field at the top level. Plano validates configs against a versioned JSON schema — an unrecognized or missing version will cause `planoai up` to fail immediately with a schema validation error before the container starts.
+
+**Incorrect (missing or invalid version):**
+
+```yaml
+# No version field — fails schema validation
+listeners:
+  - type: model
+    name: model_listener
+    port: 12000
+
+model_providers:
+  - model: openai/gpt-4o
+    access_key: $OPENAI_API_KEY
+```
+
+**Correct (explicit supported version):**
+
+```yaml
+version: v0.3.0
+
+listeners:
+  - type: model
+    name: model_listener
+    port: 12000
+
+model_providers:
+  - model: openai/gpt-4o
+    access_key: $OPENAI_API_KEY
+    default: true
+```
+
+Use the latest supported version unless you are targeting a specific deployed Plano image. Current supported versions: `v0.1`, `v0.1.0`, `0.1-beta`, `v0.2.0`, `v0.3.0`. Prefer `v0.3.0` for all new projects.
+
+Reference: https://github.com/katanemo/archgw/blob/main/config/plano_config_schema.yaml