* feat(examples): add next-runtime-snapshot Next.js example + docs

Adds examples/next-runtime-snapshot proving Next.js App Router works as a
devframe SPA via static export — three RPC functions (system / memory / env)
surface host Node runtime info, exercising static + query types and
valibot-validated args. Documents the Next.js SPA setup recipe alongside
the existing Nuxt one, broadens the pnpm frontend catalog to React + Next,
and ships vitest + Playwright coverage.

* chore(examples): address Copilot review feedback on next-runtime-snapshot

- Invalid regex pattern in `env` RPC now matches nothing rather than
  silently widening to all keys (could leak vars the redaction
  heuristic doesn't catch). Adds a vitest case to cover.
- Drop dead try/catch around `mountStaticHandler()` in test utils — it
  doesn't throw on missing distDir.
- Replace `<dl>` with `<span>` children with `<div className="kv">` in
  the system + memory cards (invalid definition-list structure).
- Add `aria-label` to the env filter input.
- Coalesce `Locator.textContent()` to `''` in the Playwright dev spec.
- Match the example's actual build script in the docs snippet
  (`mkdir -p dist` before `cp -r`).

* ci: add ecosystem test against vitejs/devtools

Pack the local devframe build, clone vitejs/devtools at its latest released
tag, override its devframe dependency via pnpm.overrides, and run the
downstream install/build/test to catch regressions before release.

Triggered manually (with an optional ref input) or on a weekly schedule.

* ci: support commit SHAs and surface spawn errors in ecosystem-ci

Switch from `git clone --branch` to `git init` + `git fetch --depth 1` so
the workflow's `ref` input accepts commit SHAs (as the description
already advertises), and include `result.error` / `result.signal` in the
thrown message so spawn failures are diagnosable.

Addresses Copilot review on #23.

* fix(devframe): cache rpc setup per-context via WeakMap

Module-level RPC defs registered into multiple contexts in the same
process (multi-server tests, hot-reload teardown/replay) previously
shared a handler closed over the first context's state. Cache by
context object so each context gets its own setup result.

* docs(devframe): document rpc/ folder + WeakMap context pattern

Skill and rpc guide now describe the one-file-per-RPC layout under
src/rpc/ and the WeakMap-based src/context.ts for sharing setup-time
state across files. All three examples adopt the pattern, with
streaming-chat demonstrating the WeakMap context for its shared
channel + history.

* refactor: nest per-rpc files under rpc/functions/

Mirrors @vitejs/devtools-kit conventions and leaves room for sibling
files like rpc/utils.ts next to rpc/index.ts as the rpc surface grows.

* fix(examples): use explicit .ts extensions on relative imports

Node native ESM (bin.mjs -> src/devframe.ts) doesn't auto-resolve
directory or extension-less imports — only the bundler-backed test
harness did. Add explicit .ts extensions so the playwright e2e
webserver can boot the examples.