fix(build): replace process.env.NODE_ENV in 1st-gen and 2nd-gen builds

[rubencarvalho]

Description

Ensures built artifacts in both 1st-gen and 2nd-gen never contain raw process.env.NODE_ENV references, so downstream consumers (e.g. Sass playground) loading SWC packages in a browser without a bundler don't hit ReferenceError: process is not defined.

• 1st-gen (ts-tools.js): adds an explicit define for process.env.NODE_ENV in the esbuild config. esbuild's build() API auto-replaces this by default, but making it explicit is defensive and self-documenting.
• 2nd-gen (vite.config.js / vite.config.ts): adds a define to the Vite config. Vite's library mode (build.lib) does not auto-replace process.env.NODE_ENV, which is why the published 2nd-gen dist/element/spectrum-element.js was shipping with the raw expression — this is the actual customer-facing bug.

Motivation and context

PR #6250 fixes ReferenceError: process is not defined for downstream consumers by adding a typeof process !== 'undefined' runtime guard in Base.ts and spectrum-element.ts. That approach fixes the symptom but breaks 1st-gen CI tests: esbuild doesn't replace typeof process, so the guard evaluates to false in the browser test environment, window.__swc is never initialized, and window.__swc.warn() crashes in components like DialogBase.

Verification — built dist files no longer contain any process.X or typeof process references:

$ grep -rEn '\bprocess\.|typeof process\b' \
    1st-gen/packages/*/src/*.dev.js 1st-gen/packages/*/src/*.js \
    1st-gen/tools/*/src/*.dev.js 1st-gen/tools/*/src/*.js \
    2nd-gen/packages/core/dist 2nd-gen/packages/swc/dist
# (no matches)

In the rebuilt 2nd-gen spectrum-element.js, the entire dev-mode setup block is dead-code eliminated because "production" === 'development' is false.

Important: PR #6250 must also revert its typeof process !== 'undefined' source-level guards in Base.ts and spectrum-element.ts. With process.env.NODE_ENV replaced at build time in both build systems, the guards are unnecessary, and keeping them would still break 1st-gen tests (the built output becomes if (typeof process !== 'undefined' && true), still false in the browser).

Related issue(s)

• Fixes the CI breakage introduced by fix(core): Check whether process is defined before trying to use it #6250
• fixes #6242

Author's checklist

• I have read the CONTRIBUTING and PULL_REQUESTS documents.
• [n/a] I have reviewed at the Accessibility Practices for this feature, see: Aria Practices
• [n/a] I have added automated tests to cover my changes.
• [n/a] I have included a well-written changeset if my change needs to be published.
• [n/a] I have included updated documentation if my change required it.

Accessibility testing checklist

N/A — build configuration change only.

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Latest commit: 89e88be

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[github-actions]

📚 Branch Preview Links

• Documentation Site (first-gen)
• Storybook (first-gen)
• Storybook (second-gen)

🔍 First Generation Visual Regression Test Results

When a visual regression test fails (or has previously failed while working on this branch), its results can be found in the following URLs:

• Spectrum | Light | Medium | LTR
• Spectrum | Dark | Large | RTL
• Express | Light | Medium | LTR
• Express | Dark | Large | RTL
• Spectrum-two | Light | Medium | LTR
• Spectrum-two | Dark | Large | RTL
• High Contrast Mode | Medium | LTR

Deployed to Azure Blob Storage: pr-6264

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