DDIR: bump corgi to one Int; Float as its own scalar

[frankmcsherry]

Corgi's #74 replaced leaf widths and integer kinds with two leaf types, Int (exact within i64) and Float (f64).
This PR moves DDIR's corgi pin past it, and then gives DDIR a Float of its own.

Bump to one Int

DDIR's Int is corgi's Int, so the sign-bit swizzles (ToSigned, signed_order_view) are gone and division and ordered compares are corgi's own.

Corgi orders integers by signed value, so arrangement identifiers are i64 throughout join, reduce, and search.
The join walk now starts at i64::MIN; starting at 0 would skip negative keys (negative_keys_join).

Corgi chooses how to hold an integer column, and a mask or sum tag may be held as bytes.
present_key widens such a key to i64, so it is its own identifier rather than hashed (byte_held_integer_keys_are_presented_as_i64).
Arranged values are widened the same way, so every chunk's lanes can be borrowed.

&& and or read each operand as 0/1 (nonzero is true) before min/max, as ir::eval does.
hash shifts with shr_b64, and a bound that is not positive reduces to the identity.
Ordered compares now lower on any two same-shape values, by corgi's structural order.

Float

Value::Float replaces the one-variant F64 newtype over an encoded Int.
It compares, orders, and hashes by the total order, as corgi's Float does, and transcodes to a corgi Float column.
float is a declarable type.
The SNB harness reads Float(x) from server output in place of the newtype's payload.

Notes

The pin is corgi 9737792, which adds #75 on top of #74: Weave reads its tags at any integer storage, so list literals tag elements with Iota.
The u64 type name is retired; int and float are the scalar types.

Checks

• cargo test --workspace; AoC 33/33 on both backends; the LDBC smoke, SNB catalogue (mixed at 1 and 4 workers, maintained at 4), and release explain suites.
• Performance, codegen-units=1, interleaved, three runs each, identical outputs: arith 2.61–2.63s → 2.61–2.82s (one outlier), reach 2.03–2.04s → 2.00–2.03s, listord 3.12–3.38s → 3.12–3.16s.

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