refactor(env): move runtime env setup to packages

[asturur]

Refactors Fabric environment setup so the core package owns only the environment holder, types, and setter/getter APIs, while the browser and node packages own their runtime-specific environment implementations.

The PR is small on purpose.
This PR is not moving core files yet and so imports from @fabric/node to src are still relative.

Key changes:

• Add setEnvFactory to the core env holder and remove browser/node runtime imports from src/env.
• Move browser env setup into packages/browser/src/env.ts and install it lazily from browser/root browser entrypoints.
• Move node env setup and NodeGLProbe into packages/node/src, keeping @fabricjs/node and fabric/node responsible for jsdom/canvas.
• Stage @fabricjs/core from a neutral core bundle so the published core package does not include runtime env implementations.
• Update generated root dist artifacts and the package changelog.

Validation:

• npm run lint passes, with existing warnings.
• npm run prettier:check is blocked locally by unrelated untracked e2e/ report files; the PR files pass oxfmt --check.
• tsc -p ./tsconfig.build.json --noEmit
• tsc -p ./tsconfig-extensions.json --noEmit
• tsc -p ./tsconfig.packages.json --noEmit
• node ./scripts/package-smoke.mjs
• rg "jsdom|from 'canvas'|src/env/node|NodeGLProbe" packages/core src/env
• Browser package import smoke without global window/document

[codesandbox]

Review or Edit in CodeSandbox

Open the branch in Web Editor • VS Code • Insiders

Open Preview

• Run Next Template
• Run Node Template
• Run Vanilla Template
• Run Vue Template

[github-actions]

Build Stats

file / KB (diff)	bundled	minified
fabric	774.150 (+0.022)	293.676 (+0.275)

[github-actions]

=============================== Coverage summary ===============================
Statements   : 79.92% ( 8047/10068 )
Branches     : 76.87% ( 4331/5634 )
Functions    : 85.53% ( 1526/1784 )
Lines        : 79.91% ( 7867/9844 )
================================================================================

[sonarqubecloud]

Quality Gate failed

Failed conditions
50.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud

[Smrtnyk]

we should also at one point move jsdom dep to the node subpackage, i guess that comes later?

[asturur]

we should also at one point move jsdom dep to the node subpackage, i guess that comes later?

I m following a plan step by step to avoid doing mess, but yes, the idea at the end is total separation for node and browser. As soon as i can do that 'fabric/node' is jut a re-export of @fabricjs/node, then i can move them.

fabric package will still be requiring those, but it will be a legacy pacakge. if you install @fabricjs/browser in theory you won't have any node dep in your logs.

[asturur]

Ok since you approved i move to next step right away.