ci: skip PR runs of workflows the change cannot affect

[napetrov]

Part of #432

Summary

pull_request touches only...          skips
bindings/c/**, examples/c/**          linux, linux-arm, macos, cpp-runtime, wheel
bindings/cpp/**                       linux, linux-arm, macos, c-api, wheel
bindings/python/**, examples/python   linux, linux-arm, macos, c-api, cpp-runtime
tests/**, benchmark/**, utils/**      c-api, cpp-runtime, wheel
**/*.md, CODEOWNERS, dependabot.yml   all six build workflows
another workflow's yml / scripts      the workflows that don't use them

• Each of the six build workflows gets a pull_request.paths-ignore list.
• push to main and workflow_dispatch are unchanged and still run everything.
• They are ignore-lists, so a path that isn't listed (a new directory, include/**, cmake/**) still triggers every workflow.
• Why the bindings can be skipped for core workflows: the root CMake project never builds bindings/; only bindings/{c,cpp} pull in the core via add_subdirectory(../..).
• Also drops -DSVS_EXPERIMENTAL_LEANVEC=YES from ARM and macOS. That option no longer exists; it is only mentioned in HISTORY.md.

Evidence

• Before: C API-only PRs ran the full x86/ARM/macOS core matrix on every push. [C API] Add logging support (logger handle) #408 is one example: 2.5k min of build-linux alone.
• After: I replayed the new filters (same glob semantics) against the changed files of every PR updated 09-16..10-16:

PR-event runner-minutes in window : 71,044
skipped by the new filters        : 12,175  (17%)
PRs where something is skipped    : #393 #403 #404 #408 #410 #411 #416 #428 #429 #430

Checks:

• PRs touching include/ or core plus bindings still run every workflow.
• pre-commit (check yaml) passes, and actionlint reports no issues.
• No required status checks are configured on main, so a skipped workflow cannot leave a PR stuck waiting on a pending check.

Merge Danger

Door: two-way

Blast Radius: CI-only

• If a listed path does in fact affect a skipped workflow, a break would surface on the next push to main instead of on the PR. The lists were derived from the CMake structure: bindings/ is not built by the root project; tests/, utils/ and benchmark/ are off unless SVS_BUILD_* are set, which the binding scripts don't do.
• If required checks are added later, any required workflow must be removed from the filters, or a skipped run will block merges.
• The job names are unchanged.

🤖 Generated with Claude Code

[ethanglaser]

Thanks for checking on this, closing in favor of #436