Fix task error handling and deduplicate task ID validation

[Copilot]

Addresses two code quality issues identified in PR review: tasks with stream errors were incorrectly marked as Completed, and task ID validation logic was duplicated across 6 handlers.

Changes

Error handling in task execution

• Track stream errors during task execution and mark tasks as Failed instead of Completed when errors occur
• Prevents conflicting terminal states where error events are emitted but task shows as successfully completed

Task ID validation

• Extract duplicated validation logic into shared parse_task_id() helper in handlers/utils.rs
• Consolidates validation across get_task, cancel_task, get_task_events, get_task_events_since, stream_task_events, and stream_task_events_resumable
• Adds unit tests for edge cases (undefined, empty, invalid UUID)

Example

Before:

// Duplicated in 6 places
if id == "undefined" || id.is_empty() {
    return Err(AppError::bad_request("..."));
}
let task_id: TaskId = id.parse().map_err(|e| ...)?;

After:

// Single shared implementation
let task_id = parse_task_id(&id)?;

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[Copilot]

Pull request overview

This PR improves task lifecycle correctness in paws_server by ensuring tasks that encounter streaming errors are terminally marked as Failed, and it reduces handler duplication by centralizing task ID validation into a shared helper.

Changes:

• Track stream errors during task execution and emit Failed (instead of Completed) when any stream error occurs.
• Add handlers::parse_task_id() to consolidate task ID validation/parsing across task and SSE endpoints.
• Add unit tests for parse_task_id() edge cases.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
crates/paws_server/src/task/manager.rs	Track stream errors and set terminal task status/event to Failed when errors occur.
crates/paws_server/src/handlers/utils.rs	New shared parse_task_id() helper plus unit tests.
crates/paws_server/src/handlers/tasks.rs	Replace duplicated ID validation/parsing with parse_task_id().
crates/paws_server/src/handlers/sse.rs	Replace duplicated ID validation/parsing with parse_task_id().
crates/paws_server/src/handlers/mod.rs	Register and re-export the new utils handler module.
Cargo.lock	Lockfile update reflecting dependency resolution (hyper entry).

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[Copilot]

This test module imports pretty_assertions::assert_eq but never uses it, which triggers an unused-import warning in tests. Remove the import or update the assertions to use it.

Suggested change

use pretty_assertions::assert_eq;

[Copilot]

TaskId is imported but not used in this module after switching to parse_task_id, which will trigger an unused-import warning. Remove the use crate::task::TaskId; import.

Suggested change

use crate::task::TaskId;

[Copilot]

last_error.unwrap() can panic if the invariants around has_error/last_error ever change (e.g., future refactors). You can simplify and harden this by removing has_error and branching on if let Some(error_msg) = last_error instead (or use expect with a clear message).