feat: add development diagnostics with separate development and production builds

[dangreen]

What

Development-only diagnostics across the core packages, delivered through a development build that sits next to the production build.

Warnings, console.warn, development build only:

• agera: a signal written while a computed is evaluating; an effect or an effect scope created while a computed is evaluating; a lifecycle listener attached to a signal that is not mountable.
• store: StaticHydrator finds no dehydrated value for a key.
• query: a cache key parameter is a function or a symbol (it serializes to null); a shard name registered twice.
• router: a path function called without a required parameter.
• intl: a message key missing in the loaded namespace; a params placeholder whose value is undefined.

kida's inject keeps its "outside of injection context" check in development only, production falls through to the TypeError from context.get. DependencyNotFound carries the full message in development and the token name in production.

How

• Every check is behind import.meta.env.DEV, which Vite replaces statically in library mode. agera, kida, store, query, router and intl build twice, NODE_ENV=development and NODE_ENV=production, into dist/index.development.js and dist/index.production.js. This mirrors the setup kida had before feat(nanoviews,kida): migrate kida and nanoviews to agera #52.
• publishConfig.exports gained the development and production conditions, default is production. Vite and webpack pick by mode, bare Node, Bun, esbuild and Rollup get production, node -C development opts in. No node condition: the old one mapped Node to the development build.
• Development-only code is a light wrapper over the production path, so the production build stays byte-identical to main after minification. Verified through Vite, webpack, esbuild and Rollup.
• Types come from one root vite-env.d.ts included through files in the root tsconfig.json, so dependent packages compiling these sources see import.meta.env.
• size-limit measures dist/index.production.js. kida and store moved to .size-limit.js with modifyEsbuildConfig defining import.meta.env.DEV as false: size-limit resolves workspace dependencies to TypeScript sources, where esbuild cannot fold the flag. The other packages keep JSON, size-limit ignores their peers.
• Benchmarks import ../agera/dist/index.production.js.
• The Next.js examples' integration mode (NANO_KIT_DEV) compiles the package sources through transpilePackages: it now skips the type check like the other example builds and defines import.meta.env.DEV as false through DefinePlugin, webpack turned import.meta.env into undefined in the server build otherwise.

Sizes

Production limits are back at the main values in every package. kida and store lost the inject message: All publics 4.7 → 4.65 kB and 5.95 → 5.9 kB Brotli.

Tests

New cases for every warning in agera, query, store and intl, and for the router path builder. The agera case for a write inside a notified effect guards the 'compute' in activeSub discriminator: notify() clears WatchingFlag on a queued effect, so the flag cannot tell a computed from an effect.

[codecov]

Codecov Report

❌ Patch coverage is 91.17647% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.85%. Comparing base (a91f3a1) to head (8f4d89b).

Files with missing lines	Patch %	Lines
packages/query/src/cache.ts	85.71%	0 Missing and 2 partials ⚠️
packages/intl/src/format/params.ts	88.88%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #236      +/-   ##
==========================================
+ Coverage   82.75%   82.85%   +0.10%     
==========================================
  Files          98       98              
  Lines        2465     2497      +32     
  Branches      521      533      +12     
==========================================
+ Hits         2040     2069      +29     
  Misses        315      315              
- Partials      110      113       +3     

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