add duration metric, tolerate missing tracepoints, ship el8 build

- Bubbles, treemap, icicle, and the live flamegraph 'b' cycle now include
  syscall duration (sum) as a third metric alongside events and bytes.
  Statsengine snapshots expose TotalLatencyNs to support this.
- AttachAll takes an optional warn callback. Production passes one so older
  kernels that lack newer tracepoints log a warning and keep going instead
  of aborting startup.
- Dockerfile.el8 + scripts/build-with-docker-el8.sh + mage buildDockerEl8
  produce ior.el8, a static binary built against Rocky Linux 8 glibc for
  RHEL/Rocky/Alma 8 hosts.
- README.md documents installing mage and the new el8 target.

1 files changed, 1 insertions, 0 deletions

diff --git a/AGENTS.md b/AGENTS.md
index 2f04060..d1b5d7f 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -17,6 +17,7 @@ If builds/tests fail with missing libbpf headers (for example `bpf/bpf.h` not fo
 ```bash
 mage build                             # Build BPF object + Go binary (all is an alias)
 mage buildDocker                       # Build ior inside a Rocky Linux 9 container (writes binary to repo root)
+mage buildDockerEl8                    # Build ior inside a Rocky Linux 8 container (writes ior.el8 to repo root)
 mage test                              # Run all tests
 TEST_NAME=TestEventloop mage testWithName  # Run specific test
 mage integrationTest                   # Build + run integration tests in parallel (parallelism capped to NumCPU)