perf(dev/lazy): fetch a lazy route in one request (reland #10789)

[h-a-n-a]

Relands #10789, which #10982 reverted.

#10982 was a temporary revert for vitejs/vite#23547. The Vite fix, vitejs/vite#23568, has now landed: Vite serves the dev runtime from the installed rolldown, instead of a copy built into Vite.

Differences from #10789

• Emitted code passes ids only: __rolldown_runtime__.requestLazy(realStableId, proxyId). The runtime builds the /@vite/lazy request in DevRuntime#loadLazyChunk. A dev server that serves the endpoint at another URL overrides that method (Vite uses it to add its base, bundledDev + non-root base: dynamic import requests /@vite/lazy without base → 404 vitejs/vite#23216).
• requestLazy skips the server only when the module and every static import it reaches already ran or have a factory in the tab (isRunnableHere). A registered factory alone is not enough: a patch can ship a module without its deps (fix(dev/lazy): ship the deps of a module that a patch shipped but never ran #11028).

Release note: pair with the next Vite release

This change needs a Vite version that includes vitejs/vite#23568. With older Vite, experimental.bundledDev breaks on every dynamic import:

TypeError: __rolldown_runtime__.requestLazy is not a function

Why older Vite breaks:

• Older Vite (8.3.1 and earlier) has its own copy of the rolldown dev runtime. That copy has no requestLazy.
• Older Vite depends on rolldown with a ~ range (~1.2.9 in 8.3.1, ~1.2.6 in 8.3.0). A ~ range accepts new patch versions.
• So if this ships in a 1.2.x patch, a fresh install of the current Vite gets this rolldown and breaks.

To avoid that, this should ship in a minor release (1.3.0), which ~1.2.x ranges do not pick up. Then the next Vite can move to ~1.3.0 together with vitejs/vite#23568.

[h-a-n-a]

• perf(dev/lazy): fetch a lazy route in one request (reland #10789) #11000 : 2 dependent PRs (#11020 , #11229 ) 👈 (View in Graphite)
• main

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