fix(plantask): resolve listed task file paths in TaskList and TaskCreate

[GaosCode]

Summary

This PR fixes a path handling bug in plantask when Backend.LsInfo returns file names or relative paths instead of full file paths.

It updates both TaskList and TaskCreate to resolve listed entries against baseDir before reading them, and aligns the plantask test backend with the documented backend contract so the failing scenario is actually covered by tests.

Problem

plantask currently assumes that Backend.LsInfo returns full file paths.

In practice, the backend contract allows FileInfo.Path to be a file name or a relative path. Because of that, TaskList may fail when it reads a listed task file directly:

TaskList read task file 1.json failed, err: file not found: /1.json

The same assumption also exists in TaskCreate when it scans LsInfo results and reads .highwatermark.

Root Cause

TaskList lists files from baseDir, but passes file.Path directly to Read without resolving it first.

That only works when LsInfo returns absolute paths. If the backend returns 1.json, TaskList does not join it with baseDir before calling Read.

TaskCreate has the same issue when handling .highwatermark.

Solution

This PR introduces a shared helper for resolving listed file paths:

• keep the path as-is when LsInfo already returns an absolute path
• join it with baseDir when LsInfo returns a file name or relative path

The same logic is applied in both places:

• TaskList when reading task files
• TaskCreate when reading .highwatermark

Test Coverage

This PR also updates the plantask test backend to return basename-style paths from LsInfo, which is closer to the documented backend behavior.

That makes the tests cover the real failing scenario instead of masking it with full paths.

Validation

Validated locally with:

go test -race ./...
go test -bench=. -benchmem -run=none ./...
golangci-lint run --timeout 5m

All passed.

Fixes #932

[CLAassistant]

All committers have signed the CLA.

[GaosCode]

Hi, this PR should be ready for review.

It fixes #932 and the local validation passed on my side. The remaining blocker seems to be maintainer review / workflow approval.

When someone has time, could you please take a look? Thank you!