v1.2.5 — rename skill flow→clawflow + template docs

Skill rename: flow → clawflow

Skill names are effectively global identifiers, so the generic flow risked
collision/ambiguity. Renamed to match the plugin id (clawflow):

• skills/flow → skills/clawflow
• openclaw.plugin.json skills path + SKILL.md frontmatter name → clawflow

Template docs: whole-payload dumps

Agents were adding a redundant code node (JSON.stringify(state.inputs) →
{{ raw_body }}) to drop a full payload into a task. Added {{ inputs }} /
{{ inputs | json }} examples (bare object refs render as JSON, not
[object Object]) and a "Common mistake" callout against serializing with a
code node.

No engine/runtime changes.