refactor!: reduce InfiniCore to a component manifest

[voltjia]

Summary

• Reduce InfiniCore to a component manifest containing only its license, manifest documentation, contribution guidelines, and the InfiniRT, InfiniOps, and InfiniCCL gitlinks.
• Pin InfiniRT at 0cdbb16967e15f2e055dea1ec9641617bf3b6cf6, InfiniOps at 94965ca433ea44b9cd4b8520a0f1d9687f81cfa9, and InfiniCCL at e8ccc0cb23ca5b1b1d63be29ba61ea031de72807.
• Remove the legacy runtime, operator, Python package, build system, tests, scripts, and repository workflows from this repository.
• Add a focused CONTRIBUTING.md for the shared component contribution conventions.

Component Revisions

• InfiniRT 0cdbb16967e15f2e055dea1ec9641617bf3b6cf6.
• InfiniOps 94965ca433ea44b9cd4b8520a0f1d9687f81cfa9 contains the unified consumer-owned ops.json implementation selector from feat(build): select operator implementations from ops.json InfiniOps#931, the TVM-FFI linked transport, and the FlashInfer TopKTopPSamplingFromLogits slot 16 provider from feat(linked): add FlashInfer sampling provider InfiniOps#930. Its ancestry does not contain native sampling PR feat(nvidia): add top-k top-p sampling provider InfiniOps#922.
• InfiniCCL e8ccc0cb23ca5b1b1d63be29ba61ea031de72807 contains bridge dependency regeneration from fix(build): regenerate communication bridge for header changes InfiniCCL#57, NCCL point-to-point communication from feat(nccl): add point-to-point communication InfiniCCL#58, and NCCL AllGather from feat(nccl): add all-gather communication InfiniCCL#59.

Motivation

InfiniCore should coordinate compatible component revisions instead of maintaining duplicate runtime and operator implementations. Keeping one authoritative implementation in each component removes the legacy API surface and makes the repository boundary explicit.

Repository Surface

The resulting repository has exactly seven tracked paths and no build or packaging entry point of its own. README.md documents the manifest role and recursive checkout, while CONTRIBUTING.md documents the contribution contract.

Breaking Change

InfiniCore no longer provides the legacy in-tree runtime, operator, build, packaging, or Python APIs. Component implementations are provided exclusively by the pinned submodules.

Validation

• Verified git ls-files returns the intended seven paths.
• Verified all component entries use gitlink mode 160000 and resolve to the revisions listed above.
• InfiniOps Release/NDEBUG build passed on A100; resolver tests passed 33/33 and FlashInfer slot 16 GPU tests passed 10/10.
• Verified the final InfiniOps SHA is based on current master, contains the rebased selector commit 87a242bac455d76dcdb5823cd201857909390a6c, and does not contain feat(nvidia): add top-k top-p sampling provider InfiniOps#922 or the superseded selector commit 4ba65cedda7c1e3d3942112de8a0117643b58306.
• Verified the Core range passes git diff --check; only the InfiniOps gitlink changed in the latest commit, while the validated InfiniCCL and InfiniRT pins remain unchanged.

The component PRs must land before this manifest is made ready for merge; the current gitlinks intentionally keep the integration reproducible while reviews proceed.

Supersedes #1405.

Closes #1373