[ASDAlexander77]

Fixes the two bugs left open by #424.

1 !== true and "a" !== 1 were false

=== / !== between a boolean, a number and a string folds to a constant in adjustTypesForBinaryOp, but the operator still runs on the replacement operands. They were (result, true), so !== computed true !== true. Both operators now get (false, true): false === true is false, false !== true is true.

The fold also missed operands typed number (isIntOrIndexOrFloat() does not match !ts.number), so const x: number = 1; x === true coerced and was true. isNumeric now includes NumberType.

A length merged with -1 returned 4294967295

function f(p: string, c: boolean) { if (c) return p.length; return -1; }   // f("abc", false) == 4294967295

canWideTypeWithoutDataLoss treats index as a signless integer, so si32 -> index counts as lossless and the merge picked index, which holds an unsigned value. The new mergeIndexWithSignedInt merges index (or a signless integer) with a signed integer into a signed integer of at least 64 bits. It runs in:

• mergeType: return types, array literals ([p.length, -1])
• findBaseType: conditionals (c ? p.length : -1), ??, generic type arguments inferred from several arguments

canCastFromTo itself is unchanged, so overload resolution and argument passing are not affected.

Decisions to check

• The merged type is si64, not TypeScript's number. That matches the existing u32 + s32 -> si64 rule in mergeIntTypes.
• The rule covers signless integers, not just index: const p = "abc"; c ? p.length : -1 folds the length to a signless i32 constant, which wrapped the same way. Side effect: a function returning a signless i32 binding (e.g. Date.getDate()) on one path and -1 on another now infers si64 instead of i32.
• On x86, index(32) + si32 also becomes si64.

Not in this PR

let x = p.length; x = -1; still prints 4294967295: the variable's type is fixed at its declaration, no merge happens.

Tests

• New: 00strict_equals_mismatched_types.ts (literals, consts, number/boolean/string-typed values; loose == still coerces) and 00length_with_negative_merge.ts (both return orders, conditionals, array literals, constant-string length), each compile + jit.
• Release suite: 3335/3335 passed (one test disabled, as before).
• DefaultLib (main b67a213) rebuilt release/gc with this compiler: 158/158 compile, 158/158 jit.
• Not run: Debug, other memory models, x86.

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