fix(router): preserve fang order

[iWhatty]

Summary

This fixes fang ordering during final router compression for single-child static chains.

Without this change, request context written by a parent fang could become invisible to a nested top-level fang on a child Ohkami after compression.

Problem

I added two regression tests (/src/ohkami/mod.rs):

• parent_context_auth_is_visible_to_nested_top_level_fang_in_realistic_order
• parent_context_auth_is_visible_to_nested_local_route_fangs_in_realistic_order

The first test failed before this change:

• a parent fang writes request context
• a nested top-level fang on a child Ohkami tries to read it
• the request was rejected as unauthorized

The second test passed:

• same parent context-writing fang
• same nested routes
• same child authorization fang, but attached locally per-route instead of as a top-level fang

This showed that the issue was specific to nested top-level fang composition, not local per-route fangs.

Root cause

In router/final.rs, compression of a node with its single static child merged fang lists in the wrong order:

• previous behavior used base.fangses.append(child.fangses)
• this made child fangs effectively wrap parent fangs after compression

That inverted the intended outer/inner behavior for compressed nested top-level fangs.

Fix

During compression, merge fang lists in the correct order so that:

• child node fangs remain inner
• base node fangs remain outer

This preserves the expected execution order and makes compressed behavior consistent with the non-compressed case.

Validation

Ran:

cargo test -p ohkami parent_context_auth_is_visible_to_nested_ --lib --features rt_tokio -- --nocapture
cargo test -p ohkami --lib --features rt_tokio

Both regression tests pass, and the relevant ohkami library test suite passes as well.

[kanarus]

@iWhatty

• After further thought, the root cause wasn't actually the fangs order during compression, but rather a bug in router::base::Router::apply_fangs itself (which is called from Ohkami::into_router).
• Thanks for catching this! Your feedback helped me realize that the logic for adding fangs in apply_fangs shouldn't just be a simple push; they actually need to be added to the outside.
• Since this wasn't an issue with your code, I went ahead and committed the fix myself.

[kanarus]

👍