[AI] Fix Typos

[KCarretto]

This PR fixes spelling errors in AGENTS.md and Go source files.
Specifically:

• AGENTS.md: "reuseable" -> "reusable"
• tavern/config.go: "behaviour" -> "behavior" (in comment)
• tavern/internal/errors/http_test.go: "behaviour" -> "behavior" (in comment)

Ran go fmt ./... and go test ./... to ensure correctness.

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PR created automatically by Jules for task 14906559020994278372 started by @KCarretto

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[github-actions]

Summary

Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
2564    ±0	2564    ±0	0    ±0	0    ±0	0    ±0	0    ±0	1ms    ±0

Previous Results

Build 🏗️	Result 🧪	Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
#951	✅	2564	2564	0	0	0	0	18.1s

Insights

Average Tests per Run	Total Flaky Tests	Total Failed	Slowest Test (p95)
2564	0	0	5.2s

Slowest Tests

Test 📝	Results 📊	Duration (avg) ⏱️	Duration (p95) ⏱️
eldritch-libsys: std::dll_inject_impl::tests::test_dll_inject_simple	1	5.2s	5.2s
imix::bin/imix: install::tests::test_install_execution	3	1.1s	3.3s
imix::bin/imix: install::tests::test_install_execution	3	1.1s	3.3s
imix::bin/imix: install::tests::test_install_execution	3	1.1s	3.3s
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_streaming_error	3	3.0s	3.0s
imix::bin/imix: tests::task_tests::test_task_streaming_error	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.}

Github Test Reporter by CTRF 💚