fix(skill): tail_file test uses OS-specific absolute path

[anrenlx2025]

Cross-platform fix for TestTailFile_Execute_NotFound. Independent of the Windows edge PR chain (#228 / #229 / #230).

Problem

The test hardcoded /tmp/this-file-does-not-exist-ongrid-test as a non-existent absolute path. On Windows /tmp/... is not absolute (Windows requires a C:\-style drive prefix), so filepath.IsAbs returns false, the test gets "path must be absolute" instead of the expected file-not-found error, FAIL on Windows.

Fix

Use filepath.Join(os.TempDir(), "..."):

• Linux/macOS: /tmp/this-file-does-not-exist-ongrid-test
• Windows: C:\Users\<user>\AppData\Local\Temp\this-file-does-not-exist-ongrid-test

Both satisfy filepath.IsAbs, preserving the original test intent.

Scope

1 file, 3 insertions / 1 deletion. Test-only change, no production code touched.

Verification

• go test -run TestTailFile_Execute_NotFound ./internal/skill/builtin/ passes on Windows
• Full go test ./internal/skill/builtin/ passes

Why independent PR

Discovered while running PR3 Windows tests, but the bug and fix are platform-wide (not Windows-edge specific). Keeping it independent lets it merge quickly without waiting for the Windows edge chain (which will take 1-2 months to review).

Contribution

• I have read and agree to the project contribution guide. Guide: https://github.com/ongridio/ongrid/blob/main/CONTRIBUTING.md

[singchia]

Thanks for the focused test portability fix. The change itself looks reasonable, but this PR is currently BLOCKED and has no CI results. Please rebase it onto the latest main and restore the required checks; once the test suite is green, this can be reviewed and merged independently of the Windows Edge stack.

[anrenlx2025]

@singchia Rebased onto ongridio/ongrid@efc0ddb (was 106 behind). Diff unchanged: 1 file, +3/-1 (internal/skill/builtin/tail_file_test.go).

Local verification:

• ✅ go test ./internal/skill/builtin/ — Windows native PASS (5 tests)
• ✅ GOOS=linux go build ./internal/skill/builtin/ — exit 0
• ✅ GOOS=linux go vet ./internal/skill/builtin/ — exit 0
• ✅ GOOS=linux go test -c — exit 0

CI status: Workflow runs are in action_required state (fork PR default). Could you approve the CI run for this PR? Once approved, the test-only
3-line change should pass quickly. This PR is independent of the Windows edge stack (#228/#229/#230) per your earlier guidance.

[singchia]

The cross-platform direction is right. Please use a test-owned directory instead of a fixed filename under os.TempDir():

notExistPath := filepath.Join(t.TempDir(), "missing.log")

os.TempDir()/this-file-does-not-exist-ongrid-test can already exist because of another test run or a user-created file, which makes this specific not-found assertion flaky. t.TempDir() keeps the Windows absolute-path fix and guarantees the target has not been created.