add Dockerfile and Rocky Linux 9 build docs

Introduces a Docker-based build path so ior can be compiled on any
Linux host without a native Rocky 9 toolchain setup:

- Dockerfile: Rocky 9 minimal image with Go (version from ARG, default
  from go.mod), static libelf/libzstd built from source, libbpfgo at
  v0.9.2-libbpf-1.5.1, and mage; CMD runs mage generate + mage all
  against the repo root mounted as a volume.
- scripts/build-with-docker.sh: reads GO_VERSION from go.mod, passes it
  as --build-arg to docker build, mounts tracefs and BTF into the
  container, writes the binary to the repo root.
- Magefile.go: adds BuildDocker target that wraps the script.
- README.md: simplified to the two build paths (Docker + native) with
  links to docs/; removed GOTOOLCHAIN=auto throughout.
- docs/build-rocky-linux-9.md: full manual Rocky 9 steps, libbpfgo
  toolchain setup/rollback, compile-once-run-everywhere explanation,
  and timing semantics.
- docs/tui-reference.md: complete TUI hotkey reference, recording mode
  details, and the .ior.zst vs Parquet trade-off table.
- AGENTS.md: removed GOTOOLCHAIN=auto from all build commands.
- internal/c/generated_tracepoints.c: regenerated against the host kernel.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

0 files changed, 0 insertions, 0 deletions