feat: add Start development toolbar and server function inspector

[birkskyum]

Waiting for:

• Publishing https://github.com/solidjs/solid-start-devtools as @solidjs/start-devtools

Summary

• add the Start development toolbar, runtime error overlay, and server function inspector
• keep the browser UI in @solidjs/start-devtools
• keep Vite-specific injection and lifecycle wiring in this plugin
• support generated and authored client entries
• detect the optional devtools package automatically
• support start.devtools: true to require it and false to disable it
• keep the toolbar out of production builds

Package split

The toolbar UI and browser runtime live in solidjs/solid-start-devtools and will be published as @solidjs/start-devtools.

This PR is the Start-mode adapter. It provides the development-only virtual modules, injects the toolbar into generated or authored client entries, and connects the server-function observer.

The devtools package is an optional peer dependency. Start projects can install it as a development dependency, while other users of the Vite plugin do not receive its UI dependencies. When the package is absent the toolbar stays off. Explicitly setting start.devtools: true reports a clear setup error if it is missing.

The development dependency and lockfile are prepared for @solidjs/start-devtools@1.0.0-next.0. CI installation will remain blocked until that version is published.

Context

This ports the toolbar work from the SolidStart v2 migration and follows the inspector implementation from solid-start#2049.

Server function call data depends on dom-expressions#570 and a subsequent Solid package refresh. The runtime error viewer works independently.

Testing

• plugin build and type declarations
• package checks, 100/100
• automatic mounting when the optional package is installed
• no injection when the package is absent
• clear error when start.devtools: true is used without the package
• no devtools code in the production output
• existing Start client, production, and middleware suites

[changeset-bot]

🦋 Changeset detected

Latest commit: 8a3ae45

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@solidjs/vite-plugin	Minor

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commit: 8a3ae45

[ryansolid]

Landing this with post-review fixes applied on top (8a3ae45), verified against the now-published @solidjs/start-devtools@1.0.0-next.0:

• Bare-import resolution (blocker): the virtual devtools modules imported @solidjs/start-devtools by bare name, which Vite could only resolve from the app root — broken for pnpm-isolated installs where the only copy is the plugin's materialized optional peer in .pnpm. Detection now captures the package's resolved id (app graph first, plugin's own location as a fallback) and resolveId delegates the virtual modules' imports to that exact resolution. Repro'd both ways with packed tarballs: a workspace app with the transitive-only copy 500s on the PR head ("start.devtools requires @solidjs/start-devtools" despite it being installed) and works after the fix, with the import visibly delegated via /@fs/.
• Cold first touch: load() for the virtual modules now runs detection itself, so a direct request before the entry has loaded doesn't error.
• No mid-session reload: the toolbar graph hangs off virtual modules the dep scanner never crawls, so its first-request discovery re-optimized deps and full-reloaded the page. When the package is root-reachable it (plus @solidjs/web/server-functions) is pre-bundled at scan time, mirroring the refresh-runtime precedent.
• Windows: the authored-entry transform compares module ids against path.resolve output — both sides now go through Vite's normalizePath.
• Lockfile: the committed integrity hash matches the real published tarball (verified by a fresh registry install). pnpm-workspace.yaml gains the minimumReleaseAgeExclude entry the fresh publish needs.
• e2e: start-ssr grows 8 devtools assertions — dev asserts the generated-entry DevToolbar wrap, the observer wiring, and the mounted toolbar in the live DOM (hydration stays clean); an SSR_DEVTOOLS=0 sub-run asserts the opt-out; prod asserts grep-clean client/server bundles and a toolbar-free DOM.
• Changeset reworded to name the option (start.devtools) and its semantics.

Full local gate green: start-ssr 357/357 + http-bridge 10/10, start-client 46/46 (incl. this PR's toolbar/error-viewer checks), css-matrix 82/82 + bridge 19/19, build + tsc + package-check clean.

Thanks @birkskyum — the toolbar itself worked great in testing; hydration is clean with the DevToolbar wrap and the server-function inspector picks up live calls.