test(awk): add rewritten oracle harness

[matt-dz]

Summary

Adds the rewritten AWK scenario harness and pinned GNU awk 5.4.0 oracle that future rshell awk implementation PRs build on. The harness keeps implementation gating opt-in through enabled.txt, runs rshell through an awk-shaped adapter, and preserves upstream provenance without requiring live upstream test fetches.

• Adds local rewritten AWK scenarios plus an upstream mapping ledger.
• Adds tools/awk-harness with pinned GNU awk install support and the rshell-awk adapter.
• Wires Make/CI entry points for metadata checks and rewritten scenario runs.
• Adds the implement-awk skill and compatibility guidance for future work.

Validation

• bash -n tools/awk-harness/*.sh tools/awk-harness/rshell-awk
• go test ./tests -run TestAwkScenarioMetadata -count=1
• make test_awk_rewritten

[AlexandreYang]

Topic from slack:

I'm wondering if could just compare to mawk already available in debian:bookworm-slim that we already use:

docker run --rm debian:bookworm-slim bash -c 'awk -W version'
random-funcs:       srandom/random
regex-funcs:        internal
compiled limits:
sprintf buffer      8192
maximum-integer     2147483647
mawk 1.3.4 20200120
Copyright 2008-2019,2020, Thomas E. Dickey
Copyright 1991-1996,2014, Michael D. Brennan

[AlexandreYang]

also:
I think it would be nice to make it work for scenarios tests "bash" comparison mode
which means possible installing gawk in debian:bookworm-slim or another image

[AlexandreYang]

Topic 2 from slack:

I'm not fully sure if we should just use the upstream tests suites as it,

we might have/want behaviour that slight differ from upstream awk
features that we don't implement
features we differ on purpose

---

also, beside the previous point, I believe, it's not ideal I believe to have this kind of dependency on upstream repo:

• slower CI
• less predictability, more flaky
• more complex setup

the good thing about replicating the tests as our own scenario tests is that:

• we have full control for divergent behaviour
• we can easily add more tests (if we use upstream, we can add our own scenarios tests too, but it's harder to track wasn't missing or not, and have 2 sources of tests)

[matt-dz]

Yeah, agreed that we shouldn’t run the upstream suites as-is or make them the main CI contract.

We do have harness filters, though, so I think the intended use is a curated allowlist/smoke profile: run only known-relevant upstream cases for the rshell awk subset, then translate any important discoveries into first-class tests/scenarios/ coverage.

So the split I’d suggest is:

• tests/scenarios/ stay authoritative for normal CI and intentional rshell behavior.
• The upstream harness runs filtered cases only, either opt-in, periodic, or as a small curated CI job.
• We do not depend on the moving/full upstream suite for merge correctness.
• Any upstream failure we decide matters becomes an original rshell scenario test.

That gives us the benefit of gawk coverage without the full cost/flakiness/control problem