Prevent clang-format from wrapping SPDX headers

[bdice]

The copyright notice written by rapidsai/pre-commit-hooks is 105 characters, which exceeds the ColumnLimit: 100 used by many RAPIDS C/C++ repositories. Repositories whose .clang-format has:

CommentPragmas: '^ IWYU pragma:'

can enter a loop while running pre-commit hooks:

1. verify-copyright --fix --spdx writes the canonical one-line SPDX notice.
2. On the next run, clang-format wraps that line and reflows SPDX-License-Identifier into the continuation.
3. verify-copyright restores only the copyright line, leaving reserved. before the license identifier.
4. Each subsequent run inserts another reserved. and never passes.

This has surfaced independently in several repositories:

• cuDF: Destroy RTCX cache before teardown cudf#22843
• RMM: Require C++20 rmm#2410
• cuVS: Exclude SPDX copyright lines from .clang-format NVIDIA/cuvs#2275 and Update .clang-format to fix copyright and style check NVIDIA/cuvs#2304
• RAFT: fix(clang-format): update comment pragmas for copyright notice NVIDIA/raft#3067 (landed through Fix RMAT docs NVIDIA/raft#3071)
• KvikIO: Check Direct I/O read errors before bounce copy kvikio#979 (comment)

Both RAFT's anchored pattern and cuDF's unanchored pattern protect canonical headers. We will standardize on the more conservative form:

CommentPragmas: '(IWYU pragma:|SPDX-)'

Affected repositories

• fix(clang-format): preserve SPDX comments rapids-cmake#1054
• fix(clang-format): preserve SPDX comments kvikio#1006
• fix(clang-format): preserve SPDX comments ucxx#706
• fix(clang-format): preserve SPDX comments nvforest#166
• fix(clang-format): preserve SPDX comments cuml#8368
• fix(clang-format): preserve SPDX comments cugraph#5582
• fix(clang-format): preserve SPDX comments cugraph-gnn#489
• fix(clang-format): preserve SPDX comments NVIDIA/cuopt#1560
• fix(clang-format): preserve SPDX comments rapids-logger#78
• fix(pre-commit): normalize SPDX handling NVIDIA/cuvs#2318
• fix(pre-commit): normalize SPDX handling NVIDIA/raft#3081
• fix(pre-commit): normalize SPDX handling cudf#23228
• fix(pre-commit): normalize SPDX handling rmm#2482
• fix(pre-commit): normalize SPDX handling librtcx#10
• fix(pre-commit): normalize SPDX handling rapidsmpf#1126

The cuOpt rollout also restores 51 headers that were already corrupted on main.

The cuCIM configurations use ColumnLimit: 120, an empty CommentPragmas, and no clang-format pre-commit hook, so the 105-character canonical header does not trigger this failure there.

Acceptance criteria

• Update every affected active public repository in the rollout scope still using the old pragma.
• Confirm the canonical over-column SPDX block header is unchanged by two consecutive clang-format runs.
• Confirm existing IWYU pragma: behavior remains protected.
• Check for and repair any already-corrupted reserved. ... SPDX-License-Identifier lines; the copyright hook may not detect them.