Add Effect.Console.logShow over the library Show

[biuld]

What

Effect.Console.logShow :: forall a. Show a => a -> Effect Unit, defined as
log (show value). It adds no I/O and no second stringifier: the rendering is
the library's Show, and the destination is still the one WASI.Console.log
decides. This is the wrapper #95 has been holding since the Show class landed.

Test.Assert.assertEqual/assertEqual' stay absent, and stdlib/lib/Test/Assert.purs
now records why. It is no longer a missing class — Eq and Show are both
declared — it is a compiler defect (#137).

Measured

PSRS_REQUIRE_WASMTIME=1 PSRS_ORACLE=annotations cargo test -p psrs-driver --test suite -- --ignored --nocapture, at 071fb11 plus this slice:

Board	Before	After
L1 parse	904/908	904/908
L2 failing	72/72	72/72
L3	35/48	35/48
L4	35/50	35/50
L5	53/80	53/80
passing resolved	253/413	270/413
M7 first blockers	missing 53, P10 177, P3 103, P5t 42, P5k 17, P8 13, P6 4, P0 4	missing 53, P10 187, P3 86, P5t 46, P5k 17, P8 14, P6 6, P0 4
L6/M7 runtime	0/413	0/413

logShow was the largest single P3 name blocker at 24 cases (19 reported as
"logShow is not exported by the imported module"). Of those, 17 resolve past
L2; the other 7 stop at the next P3 name, which nothing shadowed before:
Monad and compare 2 each, and negate, not, and _ 1 each. The 17 land at
later stages as 10 P10, 4 P5 typecheck, 1 P8, and 2 P6.

The assertEqual blocker

The official signature is

assertEqual' :: forall a. Eq a => Show a => String -> { actual :: a, expected :: a } -> Effect Unit

and this compiler elaborates Eq a against the record rather than a, so the
wanted constraint comes out as Eq { actual :: a, expected :: a }. Probes that
separate this from record syntax:

Signature	Result
forall a. Eq a => a -> Int	accepted
forall a. String -> { actual :: a, expected :: a } -> Int (no constraint)	accepted
forall a. { actual :: a, expected :: a } -> a — field access	accepted
forall a. { actual :: a, expected :: a } -> a — record pattern	accepted
forall a. Eq a => { actual :: a, expected :: a } -> Int	rejected
the same behind a type synonym for the record	rejected

So the record with quantified fields is fine on its own and both destructuring
forms work; only the constraint combined with the record fails. Filed as #137 with
the reproduction. Changing the argument shape would change the API the corpus
calls, so the two functions stay out — 2 passing cases remain blocked.

Validation

cargo fmt --all --check
cargo clippy --workspace --all-targets -- -D warnings
PSRS_REQUIRE_WASMTIME=1 cargo test --workspace

New execution test tests::assertions::log_show_writes_the_library_rendering
asserts the six renderings under Wasmtime, so a second stringifier would fail it.
Its negative case is written 0 - 7 rather than - 7 because unary minus still
resolves through a negate this library does not declare.

Board

Corpus cases recounted from the run above: #95 19 → 2, #94 70 → 77, #96 12 → 17,
#124 25 → 27. #94 goes up because the 7 cases that stopped on logShow stop on a
Prelude name #94 also owns.