[takeiteasy]

Run the CPU FiveAM suite on code pushes and pull requests, with two Linux SBCL jobs covering native and Lisp backends. Manual and tag runs select eight combinations across Linux x86-64, Linux ARM64 and macOS ARM64 with SBCL on every platform and ECL on macOS.

Skip docs-only changes, cancel superseded runs, build a pinned trivial-simd revision and reject backend/source mismatches. Add shared bootstrap/test scripts and document local reproduction and dependency updates. Linux SBCL uses checksummed 2.6.8 binaries; interrupted Quicklisp downloads retry up to three attempts.

Validation:

• actionlint, shell syntax, matrix selection and path-filter checks pass.
• SBCL native and Lisp each pass 136,532 checks locally. ECL native and Lisp pass with no failures.
• Clean Quicklisp bootstraps pass under SBCL and ECL. Injected FiveAM failures exit nonzero on both Lisps.
• Retry recovery, multiple return values and exhaustion pass.
• Hosted routine and eight-job manual validation pass; superseded manual-run cancellation is verified.

Linux ECL combinations are excluded from the matrix while the hosted x86-64 ECL runtime fails the threaded-executor tests with Out of bounds reference into foreign data type and even source-built ECL 24.5.10 hangs; see #35. The older-SBCL dependency loading failure is tracked separately at communal-software/trivial-simd#89. GPU suites and benchmarks are excluded.

Closes #4.