fix(harness): allow SkillLoadTool in Plan Mode by promoting isReadOnly to AgentTool interface

[chickenlj]

Summary

• SkillLoadTool implements AgentTool directly (not ToolBase), so PlanModeMiddleware's readOnlyResolver — which checked instanceof ToolBase — never recognized it as read-only, blocking load_skill_through_path calls in Plan Mode.
• Adds default boolean isReadOnly() to the AgentTool interface (returns false by default), overrides it in SkillLoadTool to return true, and updates HarnessAgent's resolver to use the interface method instead of downcasting to ToolBase.

Changes

• AgentTool.java: add default boolean isReadOnly() returning false
• ToolBase.java: add @Override to existing isReadOnly()
• SkillLoadTool.java: override isReadOnly() to return true
• HarnessAgent.java: change resolver from t instanceof ToolBase tb && tb.isReadOnly() to t != null && t.isReadOnly(); remove unused ToolBase import
• PlanModeMiddlewareTest.java: add test verifying SkillLoadTool is permitted in Plan Mode via the toolkit-based resolver

Test plan

• Existing PlanModeMiddlewareTest tests pass (7/7)
• SkillLoadToolFrontmatterViewTest passes
• New skillLoadToolIsReadOnlyAndPermittedInPlanMode test validates end-to-end: SkillLoadTool.isReadOnly() == true, toolkit resolver permits it, write_file is still denied
• mvn spotless:check clean

Closes #2056

[Copilot]

Pull request overview

This PR fixes Plan Mode’s “read-only tool” detection so tools that implement AgentTool directly (not ToolBase)—specifically SkillLoadTool / load_skill_through_path—can be permitted during Plan Mode when they declare themselves read-only.

Changes:

• Add default boolean isReadOnly() to AgentTool (default false) and align ToolBase.isReadOnly() as an override.
• Mark SkillLoadTool as read-only by overriding isReadOnly() to return true.
• Update HarnessAgent Plan Mode resolver to use AgentTool.isReadOnly() and add a regression test covering toolkit-based resolution.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
agentscope-harness/src/test/java/io/agentscope/harness/agent/middleware/PlanModeMiddlewareTest.java	Adds an end-to-end regression test ensuring SkillLoadTool is treated as read-only and permitted in Plan Mode while a mutating tool is denied.
agentscope-harness/src/main/java/io/agentscope/harness/agent/skill/runtime/SkillLoadTool.java	Declares the skill-loading tool read-only via AgentTool.isReadOnly().
agentscope-harness/src/main/java/io/agentscope/harness/agent/HarnessAgent.java	Updates Plan Mode’s read-only resolver to call AgentTool.isReadOnly() instead of downcasting to ToolBase.
agentscope-core/src/main/java/io/agentscope/core/tool/ToolBase.java	Marks existing isReadOnly() as an @Override of the new interface method.
agentscope-core/src/main/java/io/agentscope/core/tool/AgentTool.java	Introduces isReadOnly() on the interface with Javadoc and a default false implementation.

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...c/main/java/io/agentscope/core/tool/AgentTool.java	0.00%	1 Missing ⚠️
...java/io/agentscope/harness/agent/HarnessAgent.java	0.00%	1 Missing ⚠️

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