docs(opencode): update integration docs for plural dirs and new frontmatter

Reflect the switch to agents/ (plural), hex color codes, mode: subagent,
and @agent-name invocation in both the OpenCode integration README and the
main README's OpenCode section.

README.md

@@ -341,7 +341,7 @@ The Agency works natively with Claude Code, and ships conversion + install scrip
 - **[Claude Code](https://claude.ai/code)** — native `.md` agents, no conversion needed → `~/.claude/agents/`
 - **[Antigravity](https://github.com/google-gemini/antigravity)** — `SKILL.md` per agent → `~/.gemini/antigravity/skills/`
 - **[Gemini CLI](https://github.com/google-gemini/gemini-cli)** — extension + `SKILL.md` files → `~/.gemini/extensions/agency-agents/`
-- **[OpenCode](https://opencode.ai)** — `.md` agent files → `.opencode/agent/`
+- **[OpenCode](https://opencode.ai)** — `.md` agent files → `.opencode/agents/`
 - **[Cursor](https://cursor.sh)** — `.mdc` rule files → `.cursor/rules/`
 - **[Aider](https://aider.chat)** — single `CONVENTIONS.md` → `./CONVENTIONS.md`
 - **[Windsurf](https://codeium.com/windsurf)** — single `.windsurfrules` → `./.windsurfrules`
@@ -446,7 +446,7 @@ See [integrations/gemini-cli/README.md](integrations/gemini-cli/README.md) for d
 <details>
 <summary><strong>OpenCode</strong></summary>
 
-Agents are placed in `.opencode/agent/` in your project root (project-scoped).
+Agents are placed in `.opencode/agents/` in your project root (project-scoped).
 
 ```bash
 cd /your/project
@@ -455,13 +455,13 @@ cd /your/project
 
 Or install globally:
 ```bash
-mkdir -p ~/.config/opencode/agent
-cp integrations/opencode/agent/*.md ~/.config/opencode/agent/
+mkdir -p ~/.config/opencode/agents
+cp integrations/opencode/agents/*.md ~/.config/opencode/agents/
 ```
 
 Activate in OpenCode:
 ```
-Use the Backend Architect agent to design this API.
+@backend-architect design this API.
 ```
 
 See [integrations/opencode/README.md](integrations/opencode/README.md) for details.

integrations/opencode/README.md

@@ -1,9 +1,9 @@
 # OpenCode Integration
 
-OpenCode uses the same agent format as Claude Code — `.md` files with YAML
-frontmatter stored in `.opencode/agent/`. No conversion is technically
-needed, but this integration packages the agents into the correct directory
-structure for drop-in use.
+OpenCode agents are `.md` files with YAML frontmatter stored in
+`.opencode/agents/`. The converter maps named colors to hex codes and adds
+`mode: subagent` so agents are invoked on-demand via `@agent-name` rather
+than cluttering the primary agent picker.
 
 ## Install
 
@@ -13,42 +13,46 @@ cd /your/project
 /path/to/agency-agents/scripts/install.sh --tool opencode
 ```
 
-This creates `.opencode/agent/<slug>.md` files in your project directory.
+This creates `.opencode/agents/<slug>.md` files in your project directory.
 
 ## Activate an Agent
 
-In OpenCode, reference an agent by its name or description:
+In OpenCode, invoke a subagent with the `@` prefix:
 
 ```
-Use the Frontend Developer agent to help build this component.
+@frontend-developer help build this component.
 ```
 
 ```
-Activate the Reality Checker agent and review this PR.
+@reality-checker review this PR.
 ```
 
 You can also select agents from the OpenCode UI's agent picker.
 
 ## Agent Format
 
-OpenCode agents use the same frontmatter as Claude Code:
+Each generated agent file contains:
 
 ```yaml
 ---
 name: Frontend Developer
 description: Expert frontend developer specializing in modern web technologies...
-color: cyan
+mode: subagent
+color: "#00FFFF"
 ---
 ```
 
+- **mode: subagent** — agent is available on-demand, not shown in the primary Tab-cycle list
+- **color** — hex code (named colors from source files are converted automatically)
+
 ## Project vs Global
 
-Agents in `.opencode/agent/` are **project-scoped**. To make them available
+Agents in `.opencode/agents/` are **project-scoped**. To make them available
 globally across all projects, copy them to your OpenCode config directory:
 
 ```bash
-mkdir -p ~/.config/opencode/agent
-cp integrations/opencode/agent/*.md ~/.config/opencode/agent/
+mkdir -p ~/.config/opencode/agents
+cp integrations/opencode/agents/*.md ~/.config/opencode/agents/
 ```
 
 ## Regenerate