Root cause: when a file:// prompt URI resolves outside the project root, resolvePromptAppend returns the warning '[WARNING: Path rejected: $URI]' with no indication of WHY the path was rejected. Issue #3554 reports that this is confusing because the docs explicitly advertise support for absolute, home-relative, and cross-project file:// paths, yet the code intentionally restricts file:// prompt resolution to the project boundary (commit 98659783, security hardening).
Fix: extend the warning message so it now includes the resolved project root and an explicit hint that file:// prompts must reside within the project boundary. The security restriction itself is preserved unchanged.
Verification: added a regression test that asserts the rejection warning matches /outside project root/i. Test fails before the fix, passes after. Full resolve-file-uri.test.ts suite: 11 pass / 0 fail. typecheck clean.
Port devxoul's PR #821 feature to current codebase structure.
Supports absolute, relative, ~/home paths with percent-encoding.
Gracefully handles malformed URIs and missing files with warnings.
Co-authored-by: devxoul <devxoul@gmail.com>