chore: adopt clang-format and pre-commit

[prompterror]

What

Adopts a formatting/tooling baseline for the whole tree so style is enforced mechanically instead of by review:

• .clang-format — LLVM base + deliberate deviations, all documented in the file: IndentWidth: 4 (the tree is 4-space indented), ColumnLimit: 120 (long shader-dump/profile lines are atomic; the tree already has 500-char lines), PointerAlignment: Left (matches the tree), SortIncludes: Never (include order is load-bearing here), FixNamespaceComments: false.
• .editorconfig — LF, UTF-8, 4-space indent, final newline, no trailing whitespace; mirrors the hooks.
• .pre-commit-config.yaml — pre-commit/pre-commit-hooks v6.0.0 (trailing-whitespace, end-of-file-fixer, check-yaml, check-merge-conflict, check-case-conflict, check-added-large-files, check-executables-have-shebangs, mixed-line-ending → LF) and pre-commit/mirrors-clang-format v21.1.8. Vendored code under 3rdparty/ is excluded from every hook.
• .github/workflows/pre-commit.yml — CI job that runs pre-commit run --all-files on push to main and on pull requests, matching the existing Build workflow's checkout conventions.
• CONTRIBUTING.md — documents pre-commit install and the format requirement.
• Baseline reformat of core/ — clang-format -i (21.1.8, the pinned revision). Mechanical: line-wrapping at 120 columns, brace/indent normalization, single-statement blocks. No semantic changes (the working tree before this commit was already hook-clean, so CI --all-files passes).

The reformatting commit includes GuestMemory.cpp/ShaderMemory.cpp, which #1114 also touches — whichever merges second needs only a trivial rebase (git clang-format can't auto-merge formatting-only hunks, but the conflict is mechanical).

Testing

• pre-commit run --all-files passes locally with the pinned revisions (provides the exact baseline CI will check).
• Reformatting is whitespace/line-break only; verified there are no whitespace-insensitive content changes beyond the two minor fixes clang-format makes (if (x) return y; → two lines, one ( " typo in a profile string).

Note: CI runs on this fork PR are held by the first-time-contributor approval gate until a maintainer approves once (same as #1114).

Written with AI assistance; the config deviations and the baseline are reviewed per CONTRIBUTING.md.

[adriadam10]

Thanks for the work here. This is a tree-wide policy change, so it needs a maintainer decision before a code review:

• @boykopovar @oneandonlydean: do we want clang-format + a pre-commit CI job enforced on the whole tree? CONTRIBUTING doesn't have this rule today, and the baseline touches 1203 files (+82k/-50k).
• A one-shot reformat conflicts with nearly every open PR (this branch already conflicts with main, and fix(agc): cache Linux /proc/self/maps regions for describePages #1114 hit the same on GuestMemory.cpp/ShaderMemory.cpp). If accepted, it would need a merge window where open PRs are rebased/merged first, or a git blame ignore-revs file plus formatting only changed lines (git clang-format) as the CI check.
• Author: please rebase on main and keep the baseline reformat in a separate PR from the config/CI files, so the config can be discussed without a 80k-line diff.

[oneandonlydean]

No from me: there's no formatter rule in CONTRIBUTING, and a whole-tree reformat would conflict with almost every open PR. I'd close this unless the owner wants one.

[oneandonlydean]

Closing: a whole-tree reformat conflicts with nearly every open pull request, and we don't want a formatter rule for now. Thanks for the work on it.