WIP: refactor router tests

[matthewp]

Summary

• add a Router abstraction with unit tests covering routing priority and base/trailingSlash behavior
• refactor route manifest creation to accept in-memory entries for unit testing
• migrate routing integration tests to routing unit suites and remove user-route-priority fixture

Testing

• pnpm run build
• pnpm -C packages/astro exec astro-scripts test "test/units/routing/**/*.test.js" --teardown ./test/units/teardown.js

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Latest commit: c1379e4

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[matthewp]

this is not correct

[matthewp]

This should be in the manifest I think.

[matthewp]

These helpers are repeated in every test. Should this be in core routing as a utility? Is this something it would use?

Or should we have a Route type that you can do like Route.parse("/blog/[id]/post.astro") or something?

If none of the above, should these helpers be in a like a local test-helpers file?

[codspeed-hq]

Merging this PR will degrade performance by 10.5%

❌ 1 regressed benchmark
✅ 8 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	Build: hybrid site (static + server)	7.7 s	8.6 s	-10.5%

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_{Comparing refactor-analysis (c1379e4) with main (2c6484a)}