feat(workspace): support mcp configuration from workspace.json

[feloy]

• Add set_mcp_servers to the Agent trait (default no-op) so any agent can opt in to MCP configuration from .kaiden/workspace.json
• Implement set_mcp_servers for Claude: command-based servers become stdio entries, URL-based servers become sse entries, both merged into .claude.json under mcpServers
• Implement set_mcp_servers for OpenCode: command-based servers become local entries (command list = [cmd, ...args], environment map), URL-based servers become remote entries — merged into .config/opencode/config.json under mcp
• Refactor the opencode sub-modules to use a shared OPENCODE_CONFIG_FILE constant instead of the repeated path literal

Fixes #88

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 1e9a79d3-2012-497c-9e0e-24f6b689aec9

📥 Commits

Reviewing files that changed from the base of the PR and between bfcf92c and f8d2792.

📒 Files selected for processing (1)

• src/agent/opencode/mod.rs

📝 Walkthrough

Walkthrough

Adds MCP server configuration support to the agent settings pipeline. A new set_mcp_servers method is added to the Agent trait with implementations for ClaudeAgent (stdio/sse format in .claude.json) and OpencodeAgent (local/remote format in the opencode config). The opencode config path is consolidated into an OPENCODE_CONFIG_FILE constant. stage_agent_settings is updated to accept and thread MCP config from the workspace.

Changes

MCP Server Configuration

Layer / File(s)	Summary
Agent trait contract src/agent/mod.rs	Adds set_mcp_servers as a default trait method on Agent, accepting optional McpConfiguration and returning files unchanged.
OPENCODE_CONFIG_FILE constant and submodule refactor src/agent/opencode/mod.rs, src/agent/opencode/anthropic.rs, src/agent/opencode/ollama.rs, src/agent/opencode/openai.rs, src/agent/opencode/vertexai.rs	Defines OPENCODE_CONFIG_FILE constant in opencode/mod.rs and replaces all hardcoded config path strings across all opencode provider submodules and their tests.
ClaudeAgent MCP implementation and tests src/agent/claude.rs	Implements set_mcp_servers for ClaudeAgent: reads/merges .claude.json, writes stdio entries for mcp.commands and sse entries for mcp.servers, and adds unit tests covering serialization, args/env mapping, optional headers, field preservation, and merging.
OpencodeAgent MCP implementation and tests src/agent/opencode/mod.rs	Implements set_mcp_servers for OpencodeAgent: parses the opencode config, builds merged mcp object with "local" command entries and "remote" server entries (conditional environment/headers), writes back under OPENCODE_CONFIG_FILE, and adds a full test suite.
stage_agent_settings wiring and integration tests src/main.rs	Adds mcp parameter to stage_agent_settings, calls agent.set_mcp_servers, passes workspace MCP config from run, updates all existing test call sites, and adds new integration tests asserting mcpServers and mcp output for Claude and Opencode agents.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: adding MCP configuration support from workspace.json files.
Description check	✅ Passed	The description is detailed and directly related to the changeset, explaining the implementation across both Claude and OpenCode agents plus refactoring.
Linked Issues check	✅ Passed	The PR fully implements the requirements from issue #88 by reading MCP services from workspace.json and updating agent settings to configure MCP services.
Out of Scope Changes check	✅ Passed	All changes are within scope: adding set_mcp_servers to the Agent trait, implementing it for Claude and OpenCode agents, and refactoring OpenCode modules to use a shared constant.
Docstring Coverage	✅ Passed	Docstring coverage is 83.72% which is sufficient. The required threshold is 80.00%.

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[codecov]

Codecov Report

❌ Patch coverage is 98.29060% with 8 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/agent/mod.rs	0.00%	7 Missing ⚠️
src/agent/opencode/mod.rs	99.41%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

[feloy]

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/agent/opencode/mod.rs`:
- Around line 99-100: The JSON parsing fallback at the serde_json::from_str call
in the config initialization is using an empty JSON object, which loses the
$schema field when parsing fails. Instead of falling back to an empty json!({})
on parse error, identify what schema-bearing fallback is used elsewhere in the
code for missing files and apply that same fallback pattern here. Replace the
unwrap_or call to use the proper schema object instead of an empty object so the
config maintains schema consistency even when the existing content is malformed.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 74a13d3c-250d-47b8-a3f3-b9bec8e74839

📥 Commits

Reviewing files that changed from the base of the PR and between 3aef14c and bfcf92c.

📒 Files selected for processing (8)

• src/agent/claude.rs
• src/agent/mod.rs
• src/agent/opencode/anthropic.rs
• src/agent/opencode/mod.rs
• src/agent/opencode/ollama.rs
• src/agent/opencode/openai.rs
• src/agent/opencode/vertexai.rs
• src/main.rs