fix: upgrade to Fable 5.13 and Fable.Beam rc.34, emit real atoms

[dbrattli]

Summary

Upgrades to Fable 5.13.0 and Fable.Beam 5.0.0-rc.34, and fixes a silent runtime bug the upgrade surfaced.

rc.34 makes the Atom union constructor private, on purpose: because Atom is [<Erase>]d, Atom "debug" compiled to the binary <<"debug"/utf8>>, not to an atom. So this call was passing binaries where OTP expects atoms:

logger:set_primary_config(<<"level"/utf8>>, <<"debug"/utf8>>)

The result is |> ignored, so the primary log level was silently never set. All 7 call sites now use Atom.ofString, which emits erlang:binary_to_atom(<<"debug"/utf8>>).

Fable 5.13 also landed fix(beam): compile [<StringEnum>] cases to atoms instead of binaries — same class of bug. This repo has no [<StringEnum>] usage, so nothing to change there.

Why it went unnoticed

TestBeamLogger.fs is guarded by #if FABLE_COMPILER_BEAM. Under just test (.NET) that define is off, so all five Beam tests compiled down to () and passed without exercising anything. The BEAM tests could not run at all: the paket Test group only declared FSharp.Core and Fable.Core, so dotnet fable test --lang beam failed with 14 × namespace 'Beam' is not defined.

So this PR also makes them runnable:

• Fable.Beam added to the paket Test group and test/paket.references
• just build-beam / just test-beam — fable --lang beam → rebar3 compile → erl, following the same shape as Fable.Beam's own justfile
• CI now runs both suites; it previously only built

Fable.Logging.Structlog is excluded from the BEAM transpile via --exclude. Its [<Emit>] bodies contain literal Python ($0.debug($1, **$2)) which Fable emits verbatim into Erlang that does not parse. TestStructlog.fs is already #if FABLE_COMPILER_PYTHON-guarded, so nothing references the excluded module.

Verification

• just test — 49/49 on .NET
• just test-beam — 49/49 on the BEAM (locally OTP 25; CI pins OTP 27 to match Fable.Beam)
• just format-check clean
• Generated Erlang inspected to confirm erlang:binary_to_atom(...) at all call sites
• Runtime output confirms correct level mapping — =INFO REPORT=, =WARNING REPORT=, =ERROR REPORT=, =CRITICAL REPORT= — which only works with genuine atoms

Not addressed

Structlog.fs has no target guards, so referencing Fable.Logging.Structlog from a JS or BEAM Fable project produces invalid output for consumers too. Guarding it with #if !FABLE_COMPILER || FABLE_COMPILER_PYTHON would fix that at the source and make the --exclude unnecessary. Left out as a separate concern.

🤖 Generated with Claude Code