fix(harness): mark optional FilesystemTool params as required=false

[wzq-xzwj]

Summary

Several @ToolParam parameters on the harness built-in tools are documented as
optional (their descriptions say "Default: ...", "optional") and the underlying
implementation already handles missing / null / default values gracefully.
However, they are not annotated with required = false.

Because ToolParam.required() defaults to true, these parameters end up in the
generated JSON schema as required, contradicting both their descriptions and
the implementation. This misleads models into always supplying them.

Affected parameters:

Tool	Param	Description says	Was in schema
read_file	offset	"Default: 0 (from beginning)"	required
read_file	limit	"Default: 0 (all lines)"	required
grep_files	path	dir/file to search	required
grep_files	glob	"Optional file glob filter"	required
glob_files	path	base dir to search from	required
execute	working_directory	"(relative to workspace root, optional)"	required
execute	timeout	"Timeout in seconds (default: 30)"	required

Important: optional numeric params must be boxed types

Simply adding required = false to a primitive int parameter is not enough
— it introduces a runtime crash. When the model omits the argument, the framework
binds null and the reflective (MethodHandle) invocation fails with:

Cannot invoke "java.lang.Number.intValue()" because the return value of
"sun.invoke.util.ValueConversions.primitiveConversion(...)" is null

So this PR also changes read_file's offset/limit and execute's timeout
from int to Integer, applying null-safe defaults in the method body
(offset/limit -> 0, timeout -> 30). This mirrors edit_file's existing
Boolean replace_all parameter, which was already correctly boxed and optional.

Verified end-to-end: with the fix, read_file called without offset/limit
returns the file contents; before the fix it returned the intValue() NPE as a
tool error.

Implementation is already optional-safe

• LocalFilesystem.grep(...): resolvePath(rc, path != null ? path : ".")
• LocalFilesystem.glob(...): handles path == null -> falls back to cwd
• ripgrepSearch / javaSearch: if (includeGlob != null && !includeGlob.isBlank())
• LocalFilesystem.read(...): int startIdx = Math.max(0, offset), limit > 0 ? ... : all
• ShellExecuteTool.execute(...): blank working_directory skipped; timeout > 0 ? timeout : 30

Change

• Add required = false to the parameters listed above.
• Box optional numeric params (int -> Integer) with null-safe defaults.
• Formatting-only fix to SessionSearchTool so the module passes spotless:check.

Testing

• mvn -pl agentscope-harness spotless:check -> BUILD SUCCESS.
• End-to-end: agent calls read_file without offset/limit and gets file contents
  (previously crashed with an unboxing NPE).

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

❌ Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...gentscope/harness/agent/tool/ShellExecuteTool.java	50.00%	0 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!

[AgentScopeJavaBot]

🤖 AI Review

Aspect	Count
🟢 Nitpick (信息性建议，不阻塞合并)	1
🟡 Recommended (建议修复，但不阻塞合并)	2

Overall Assessment: COMMENT — Schema-only fix with correct downstream handling; minor description improvements suggested for optional params.

[AgentScopeJavaBot]

🤖 AI Review

Aspect	Count
🟢 Nitpick (信息性建议，不阻塞合并)	1
🟡 Recommended (建议修复，但不阻塞合并)	2

Overall Assessment: COMMENT — Schema-only fix with correct downstream handling; minor description improvements suggested for optional params.

[wzq-xzwj]

@jujn 请审核一下，实际使用中影响感觉还是很明显的，检查和自测均已通过。

[jujn]

@jujn 请审核一下，实际使用中影响感觉还是很明显的，检查和自测均已通过。

最近任务比较多。可能会稍晚一些。