go: lex.sx — decimal float + imaginary literals + 22 tests [consumes-lex]

Adds Go float and imaginary literal forms per Go spec § Floating-point
literals and § Imaginary literals:
  3.14   .5   1.   1e10   1.5e-3   2.0e+2   1E5    (floats)
  2i     3.14i   1e2i                              (imag)

gl-read-number! returns one of "int" / "float" / "imag"; gl-finish-number!
factors out the post-mantissa exponent + 'i' suffix logic so the int /
float / leading-dot-float paths all share it. scan! adds a .<digit>
branch ahead of the operator matcher so '.5' tokenises as float.

ASI trigger list extended to include float + imag (Go spec § Semicolons:
all literal types trigger).

Greedy-grammar pin (a single test '1.method' lexes as float ident),
since the Go spec says the '.' after a digit always belongs to the
number, never to a following identifier.

Hex floats (0x1.fp0) deferred — not commonly used.

lex 114/114.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

plans/go-on-sx.md

@@ -141,12 +141,13 @@ Progress-log line → push `origin/loops/go`.
 - [x] **Automatic semicolon insertion** (Go spec § Semicolons) — newline,
       EOF, and block-comment-with-newline trigger `;` after
       ident/int/string/rune/{break,continue,fallthrough,return}/{++,--,),],}}.
-- [ ] Float / imaginary literals
+- [x] Float / imaginary literals (decimal floats: `3.14 .5 1. 1e10 1.5e-3`;
+      imag: `2i 3.14i 1e2i`; hex floats `0x1.fp0` deferred)
 - [ ] Raw string literals `` `...` ``
 - [x] Hex/octal/binary integer literals (0x… 0o… 0b…) + underscores
       (legacy 0123 octal also accepted; consumes lex-hex-digit?)
 - [ ] Full operator set audit (47 distinct per Go spec)
-- **Acceptance:** lex/ suite at 50+ tests. Current: 92/92.
+- **Acceptance:** lex/ suite at 50+ tests. Current: 114/114.
 
 ### Phase 2 — Parser (`lib/go/parse.sx`) ⬜
 - Consume `lib/guest/core/pratt.sx` + `lib/guest/core/ast.sx`. Chisel notes
@@ -405,6 +406,12 @@ _(none yet)_
 
 _Newest first. Append one dated entry per commit._
 
+- 2026-05-27 — Phase 1 cont.: decimal float + imaginary literals.
+  `3.14`, `.5`, `1.`, `1e10`, `1.5e-3`, `2i`, `3.14i`. `gl-finish-number!`
+  handles exponent + `i` suffix; `gl-read-number!` returns the type
+  string (int/float/imag). ASI trigger list extended to float/imag.
+  Greedy-grammar pin: `1.method` lexes as `float ident`. Hex floats
+  (`0x1.fp0`) deferred. +22 tests, lex 114/114. `[consumes-lex]`.
 - 2026-05-27 — Phase 1 cont.: prefixed integer literals (`0x..`, `0X..`,
   `0b..`, `0B..`, `0o..`, `0O..`, legacy `0123`) + underscore separators
   in any digit run. Dispatch in `gl-read-number!`; consumes