feat(http/unstable): add radix tree router; keep linear scan as routeLinear

[esroyo]

Add routeRadix(), a radix tree router that provides O(segments) dispatch for static, parametric, and wildcard routes. Routes with complex URLPattern syntax (regex constraints, optional groups, inline wildcards, modifier suffixes) fall back to linear matching while preserving insertion order.

• routeRadix: radix tree with fallback to linear for complex patterns
• routeLinear: the original linear scan, extracted as its own export
• route: re-exported alias for routeRadix (backward compatible)

The radix router matches routeLinear semantics exactly; insertion order is always respected, even when static and parametric routes overlap at the same tree depth.

Benchmarks show 1.5–9x improvement on static/parametric/wildcard routes, with negligible overhead on complex fallback patterns.

---

---
config:
    themeVariables:
        xyChart:
            plotColorPalette: "#e05c5c, #4a90d9"
---
xychart-beta
    title "route: 🔴 linear vs 🔵 radix - Avg latency (µs)"
    x-axis [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
    y-axis "Avg latency (µs)" 0 --> 7

    line [0.91, 2.04, 6.1, 1.63, 5.54, 1.49, 2.84, 1.08, 3.15, 0.9, 1.45, 1.98]
    line [1.08, 1.38, 1.39, 0.62, 0.61, 1.55, 1.66, 0.91, 1.73, 1.46, 1.62, 2.1]

Loading

#	Group	🔴 linear (µs)	🔵 radix (µs)
1	static route — first in small table	0.91	1.08
2	static route — last in small table	2.04	1.38
3	static route — last in large table	6.1	1.39
4	static route — miss (small table)	1.63	0.62
5	static route — miss (large table)	5.54	0.61
6	parametric route — single param	1.49	1.55
7	parametric route — two params (nested)	2.84	1.66
8	parametric route — method mismatch	1.08	0.91
9	wildcard route	3.15	1.73
10	complex — regex constraint	0.9	1.46
11	complex — optional group	1.45	1.62
12	complex — inline wildcard with suffix	1.98	2.1

---

    CPU | AMD Ryzen 7 PRO 6850U with Radeon Graphics
Runtime | Deno 2.7.9 (x86_64-unknown-linux-gnu)

file:///../denoland/std/http/unstable_route_bench.ts

| benchmark   | time/iter (avg) |        iter/s |      (min … max)      |      p75 |      p99 |     p995 |
| ----------- | --------------- | ------------- | --------------------- | -------- | -------- | -------- |

group static route — first in small table
| linear      |        921.1 ns |     1,086,000 | (869.7 ns …   1.4 µs) | 921.5 ns |   1.4 µs |   1.4 µs |
| radix       |          1.1 µs |       885,100 | (  1.1 µs …   1.3 µs) |   1.1 µs |   1.3 µs |   1.3 µs |

summary
  linear
     1.23x faster than radix

group static route — last in small table
| linear      |          2.0 µs |       494,200 | (  2.0 µs …   2.6 µs) |   2.0 µs |   2.6 µs |   2.6 µs |
| radix       |          1.3 µs |       751,200 | (  1.3 µs …   1.7 µs) |   1.3 µs |   1.7 µs |   1.7 µs |

summary
  linear
     1.52x slower than radix

group static route — last in large table
| linear      |          5.9 µs |       170,100 | (  5.8 µs …   6.1 µs) |   5.9 µs |   6.1 µs |   6.1 µs |
| radix       |          1.3 µs |       750,600 | (  1.3 µs …   1.6 µs) |   1.3 µs |   1.6 µs |   1.6 µs |

summary
  linear
     4.41x slower than radix

group static route — miss (small table)
| linear      |          1.7 µs |       596,400 | (  1.6 µs …   2.1 µs) |   1.7 µs |   2.1 µs |   2.1 µs |
| radix       |        622.6 ns |     1,606,000 | (600.0 ns … 702.4 ns) | 621.7 ns | 702.4 ns | 702.4 ns |

summary
  linear
     2.69x slower than radix

group static route — miss (large table)
| linear      |          5.6 µs |       179,100 | (  5.4 µs …   5.9 µs) |   5.6 µs |   5.9 µs |   5.9 µs |
| radix       |        606.1 ns |     1,650,000 | (594.0 ns … 641.1 ns) | 610.5 ns | 641.1 ns | 641.1 ns |

summary
  linear
     9.21x slower than radix

group parametric route — single param
| linear      |          1.5 µs |       645,600 | (  1.5 µs …   1.7 µs) |   1.6 µs |   1.7 µs |   1.7 µs |
| radix       |          1.5 µs |       649,500 | (  1.5 µs …   1.9 µs) |   1.5 µs |   1.9 µs |   1.9 µs |

summary
  linear
     1.01x slower than radix

group parametric route — two params (nested)
| linear      |          2.8 µs |       360,900 | (  2.7 µs …   2.9 µs) |   2.8 µs |   2.9 µs |   2.9 µs |
| radix       |          1.6 µs |       614,300 | (  1.6 µs …   1.7 µs) |   1.7 µs |   1.7 µs |   1.7 µs |

summary
  linear
     1.70x slower than radix

group parametric route — method mismatch
| linear      |          1.1 µs |       924,900 | (  1.0 µs …   1.4 µs) |   1.1 µs |   1.4 µs |   1.4 µs |
| radix       |        929.0 ns |     1,076,000 | (900.7 ns … 980.0 ns) | 933.5 ns | 980.0 ns | 980.0 ns |

summary
  linear
     1.16x slower than radix

group wildcard route
| linear      |          3.2 µs |       314,400 | (  3.1 µs …   3.6 µs) |   3.2 µs |   3.6 µs |   3.6 µs |
| radix       |          1.7 µs |       600,900 | (  1.6 µs …   2.0 µs) |   1.7 µs |   2.0 µs |   2.0 µs |

summary
  linear
     1.91x slower than radix

group complex — regex constraint
| linear      |        947.0 ns |     1,056,000 | (908.1 ns …   1.3 µs) | 947.5 ns |   1.3 µs |   1.3 µs |
| radix       |          1.5 µs |       673,300 | (  1.4 µs …   1.7 µs) |   1.5 µs |   1.7 µs |   1.7 µs |

summary
  linear
     1.57x faster than radix

group complex — optional group
| linear      |          1.5 µs |       680,000 | (  1.4 µs …   1.7 µs) |   1.5 µs |   1.7 µs |   1.7 µs |
| radix       |          1.6 µs |       625,800 | (  1.6 µs …   1.8 µs) |   1.6 µs |   1.8 µs |   1.8 µs |

summary
  linear
     1.09x faster than radix

group complex — inline wildcard with suffix
| linear      |          1.9 µs |       529,200 | (  1.8 µs …   2.1 µs) |   1.9 µs |   2.1 µs |   2.1 µs |
| radix       |          2.0 µs |       490,400 | (  2.0 µs …   2.2 µs) |   2.0 µs |   2.2 µs |   2.2 µs |

summary
  linear
     1.08x faster than radix

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[codecov]

Codecov Report

❌ Patch coverage is 92.25352% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.40%. Comparing base (1cd63ca) to head (d522ffa).

Files with missing lines	Patch %	Lines
http/unstable_route.ts	92.25%	6 Missing and 5 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7075      +/-   ##
==========================================
- Coverage   94.41%   94.40%   -0.01%     
==========================================
  Files         630      630              
  Lines       50490    50617     +127     
  Branches     8949     8988      +39     
==========================================
+ Hits        47669    47786     +117     
- Misses       2249     2255       +6     
- Partials      572      576       +4     

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