Phase E: action-language tool vocabulary

Replace Claude-Code-specific tool names in skill prose, prompt
templates, and OpenCode-facing docs with action-language descriptions
that resolve to each runtime's native tool via the per-platform refs.

Changes by category:

- Prose mentions ("Use TodoWrite to track...", "Use Task tool with
  general-purpose type") → action language ("Track each item as a
  todo", "Dispatch a general-purpose subagent")

- Prompt template headers (6 files): "Task tool (general-purpose):"
  → "Subagent (general-purpose):" — preserves the type information
  without naming Claude Code's specific dispatch tool

- DOT flowchart node labels: "Invoke Skill tool" → "Invoke the
  skill"; "Create TodoWrite todo per item" → "Create a todo per
  item"

- OpenCode INSTALL.md and docs/README.opencode.md: replace the old
  "TodoWrite → todowrite, Task → @mention" mapping (which both
  taught a vocabulary skills no longer use AND was wrong about
  @mention being a real OpenCode syntax) with an action-language
  mapping verified against the installed OpenCode CLI's tool
  inventory.

The platform-tools refs landed in Phase B already document each
runtime's resolution; skills now speak in the actions those refs
map. Tool names that genuinely belong only in the per-platform
dispatch section ("In Claude Code: Use the `Skill` tool") and the
Claude-Code-specific Bash run_in_background flag note in
visual-companion remain — those are intentional carve-outs.

skills/requesting-code-review/code-reviewer.md

@@ -5,7 +5,7 @@ Use this template when dispatching a code reviewer subagent.
 **Purpose:** Review completed work against requirements and code quality standards before it cascades into more work.
 
 ```
-Task tool (general-purpose):
+Subagent (general-purpose):
   description: "Review code changes"
   prompt: |
     You are a Senior Code Reviewer with expertise in software architecture,