feat: add diffs field to Quest GraphQL type

[KCarretto]

This PR addresses the request to add a computed diffs field to the GraphQL Quest type.

Key changes:

• Added a diffs: [TaskDiff!]! field to the Quest type in quest.graphql.
• Defined TaskDiff which contains grouped ids: [ID!]!, output: String, and error: String.
• Implemented the Diffs resolver in quest.resolvers.go which groups tasks based on their output and error values after whitespace trimming.
• Ensured deterministic ordering of the output diffs array by sorting based on the first ID in the grouped IDs slice.
• Implemented test cases in TaskDiff.yml for the new resolver, covering the new computed fields and edge cases with whitespace trimming and NULL handling.

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PR created automatically by Jules for task 3358022832479564678 started by @KCarretto

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[github-actions]

Summary

Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
2841    ±0	2835    ±0	0    ±0	6    ±0	0    ±0	0    ±0	1ms    ±0

Previous Results

Build 🏗️	Result 🧪	Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
#1864	✅	2841	2835	0	6	0	0	37.5s

Insights

Average Tests per Run	Total Flaky Tests	Total Failed	Slowest Test (p95)
2841	0	0	5.1s

Test Changes

0 test added, 0 removed

Slowest Tests

Test 📝	Results 📊	Duration (avg) ⏱️	Duration (p95) ⏱️
eldritch-libsys: std::dll_inject_impl::tests::test_dll_inject_simple	1	5.1s	5.1s
TestInteractiveShell	1	5.1s	5.1s
TestOtherStreamOutput	1	5.0s	5.0s
imix::bin/imix: tests::task_tests::test_task_streaming_output	3	3.0s	3.0s
imix::bin/imix: tests::task_tests::test_task_streaming_output	3	3.0s	3.0s
imix::bin/imix: tests::task_tests::test_task_streaming_output	3	3.0s	3.0s
imix::bin/imix: tests::task_tests::test_task_eprint_behavior	3	3.0s	3.0s
imix::bin/imix: tests::task_tests::test_task_eprint_behavior	3	3.0s	3.0s
imix::bin/imix: tests::task_tests::test_task_eprint_behavior	3	3.0s	3.0s
imix::bin/imix: tests::task_tests::test_task_streaming_error	3	3.0s	3.0s

_{🎉 No failed tests in this run. | 🍂 No flaky tests in this run.}

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