fix: consider basePath when generating slide URLs

[coaxial]

Hello,

This fixes an issue with the presenter when using build --base=/path/ where the presenter will instead generate slide links as /<slide number> instead of /path/<slide number>.

I've added a test as well but getting this error when trying to run the test suite:

$ pnpm test

> @52.9.1 test /home/pierre/code/slidev
> vitest test


 DEV  v4.0.8 /home/pierre/code/slidev

 ✓ test/transform-magic-move.test.ts (2 tests) 537ms
   ✓ basic  381ms
 ✓ test/parser.test.ts (74 tests) 114ms
 ✓ packages/parser/src/timesplit/timesplit.test.ts (1 test) 16ms
 ✓ test/transform.test.ts (8 tests) 18ms
 ✓ packages/parser/src/timesplit/timestring.test.ts (2 tests) 9ms
 ✓ test/transform-all.test.ts (1 test) 12ms

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Failed Suites 1 ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯

 FAIL  test/utils.test.ts [ test/utils.test.ts ]
Error: Cannot find module '#slidev/slides' imported from '/home/pierre/code/slidev/packages/client/logic/slides.ts'
 ❯ packages/client/logic/slides.ts:2:24
      1| import type { SlideRoute } from '@slidev/types'
      2| import { slides } from '#slidev/slides'
       |                        ^
      3| import { computed, watch, watchEffect } from 'vue'
      4| import { useNav } from '../composables/useNav'
 ❯ test/utils.test.ts:4:1

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯[1/1]⎯


 Test Files  1 failed | 6 passed (7)
      Tests  88 passed (88)
   Start at  21:40:47
   Duration  1.99s (transform 557ms, setup 0ms, collect 1.29s, tests 706ms, environment 2ms, prepare 66ms)

I haven't changed this import and without my patch (i.e. just after cloning), the tests run fine.

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commit: 9da4be9