feat: result_v2 with tests

[second-ed]

No description provided.

[codspeed]

Merging this PR will improve performance by 12.48%

⚡ 2 improved benchmarks
❌ 1 (👁 1) regressed benchmark
✅ 18 untouched benchmarks

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	test_ok_and_then_chain	53.7 µs	33.5 µs	+60.6%
⚡	test_err_creation	4.8 ms	3.8 ms	+27.19%
👁	test_err_map_short_circuit	39.5 µs	56.7 µs	-30.34%

Tip

Curious why performance improved? Comment @codspeedbot explain why performance improved on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing feat/new_result (1669e30) with dev (54b56db)}

[second-ed]

Merging this PR will improve performance by 12.07%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.
Open the report in CodSpeed to investigate

⚡ 2 improved benchmarks ❌ 1 (👁 1) regressed benchmark ✅ 18 untouched benchmarks

Performance Changes

Benchmark BASE HEAD Efficiency
⚡ test_ok_and_then_chain 53.7 µs 33.6 µs +59.75%
⚡ test_err_creation 4.8 ms 3.8 ms +27.51%
👁 test_err_map_short_circuit 39.5 µs 57.1 µs -30.9%
Tip

Curious why performance improved? Comment @codspeedbot explain why performance improved on this PR, or directly use the CodSpeed MCP with your agent.

Comparing feat/new_result (776c353) with dev (54b56db)

This is from casting the return self in the Err.map method. Type-safety is likely more important than the perf regression