test: split 50-smoke.sx into per-section examples + add errors smoke

Break the monolithic examples/50-smoke.sx into 30 focused per-section examples,
filed into their category blocks (basic/types/comptime/memory/protocols/ffi),
each carrying only the top-level decls its section references (the protocols
section keeps the full preamble — its deps flow through UFCS method calls that
name-based extraction can't see). Outputs verified identical to the original
section blocks.

Add examples/1036-errors-failable-smoke.sx — an end-to-end error-handling example
(the E5.4 work): named + inferred error sets consumed via destructure, try (in
helpers), catch (bare-expr / match-body / diverging / no-binding), or
value-terminator, onfail+defer interleave, and error.X value + {} tag
interpolation.

Remove examples/50-smoke.sx. Suite: 324 passed, 0 failed.

examples/expected/0026-basic-operators.stdout

@@ -0,0 +1,60 @@
+=== 2. Operators ===
+add: 7
+sub: 7
+mul: 42
+div: 5
+mod: 2
+neg: -5
+eq: true
+neq: true
+lt: true
+gt: true
+le: true
+ge: true
+chain: true
+chain-gt: true
+chain-mixed: true
+eq-chain: true
+eq-chain-f: false
+band: 15
+bor: 7
+bxor: 240
+bxor2: 5
+bnot: -1
+bnot2: -2
+shl: 16
+shr: 16
+shl2: 24
+shr2: 127
+band-var: 15
+bor-var: 7
+bxor-var: 240
+shl-var: 16
+shr-var: 15
+bnot-var: -16
+and-assign: 15
+or-assign: 255
+xor-assign: 240
+shl-assign: 256
+shr-assign: 16
+mod-var: 2
+and: true
+and-false: false
+or: true
+or-false: false
+short-and: false
+short-or: true
+ca+=: 15
+ca-=: 12
+ca*=: 24
+ca/=: 4
+prec1: 14
+prec2: 20
+xx-cast: 200
+widen-u8-s64: 200
+widen-s32-f64: 42.000000
+widen-f32-f64: 1.500000
+widen-u8-s16: 100
+xx-s64-s32: 12345
+xx-f64-f32: 1.500000
+xx-f64-s32: 7