chore: normalize SPDX source copyright headers

[ibgreen-openai]

Goals

• Make luma.gl source-file licensing and copyright ownership machine-readable without inventing third-party authorship.
• Preserve existing RAPIDS attribution and accurately describe independently licensed upstream material.
• Keep unresolved mixed-license cases visible instead of incorrectly stamping them as MIT-only.

Changes

• Normalize existing first-party // Copyright (c) vis.gl contributors comments into SPDX-FileCopyrightText declarations throughout already-licensed source files.
• Add complete MIT/SPDX headers to 30 previously unlabeled, demonstrably first-party production module sources, including the ANARI package and malformed legacy headers.
• Preserve additional, genuine copyright holders for Mapbox, three.js authors, Gregg Tavares, and Mohamad Moneimne and Contributors.
• Correct Mapbox earcut's invalid MIT and ISC expression to MIT AND ISC, preserving its complete existing ISC notice.
• Correct PBR documentation to reference the historical MIT-licensed Khronos shader snapshot rather than the upstream project's later Apache license.
• Document the header convention in AGENTS.md.
• Add a Node-only repository-wide guard covering every existing SPDX-licensed source, every first-party production module, multiple PBR owners, the earcut ISC notice, stale exceptions, and new unstaged source files.

Explicit exclusions

• modules/effects/src/passes/postprocessing/fxaa/fxaa.ts: existing NVIDIA BSD/Cesium Apache material requires separate mixed-license remediation.
• Three engine geometry files identify Google/BSD or PhiloGL provenance that needs a dedicated ownership review.
• modules/text/src/fonts/helvetiker.ts: embedded MAGENTA/MgOpen font data carries additional non-MIT conditions.
• modules/webgl/src/context/debug/spector-types.ts: copied Spector.js declarations do not identify a sufficiently precise upstream copyright holder.
• Existing unlicensed examples, website fixtures, scripts, generated bundles, and vendored sources were not blindly assigned MIT ownership.

Verification

• nvm use
• yarn lint fix
• Focused SPDX and RAPIDS regression tests: 14 passing tests.
• yarn build
• yarn test-node: 874 passing tests, including the required pre-commit hook.
• yarn test: the Node phase passes locally; the unsharded local Chromium runner disconnects after 916 passing browser tests. GitHub Actions runs the complete browser/WebGPU coverage in three independent shards; all seven checks passed on the initial PR revision and are rerunning after review feedback.
• yarn website:build: passed; validated 474 raw documentation pages.
• (cd website && yarn build): passed; validated 474 raw documentation pages independently.
• Audited every modified source hunk: source changes are confined to file-header comments; generated, vendored, third-party, and explicitly deferred files remain unchanged.

Risks and follow-up

• This is intentionally a large mechanical source-header change; no runtime implementation or shader body changes are included.
• GitHub's web UI displays only the first 300 changed files; inspect the full deterministic change with git diff master...HEAD or the paginated pull-request files API.
• The five mixed-license source files and headerless Spector.js fork remain explicit, self-expiring test exceptions pending separate package-level legal remediation.
• @math.gl/geoarrow already included Mapbox ISC material; package-level license metadata can be evaluated separately from this source-header correction.

[chatgpt-codex-connector]

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