[P3] Lexer: colon descriptions hide valid ts-expect-error and ts-ignore directives #3488

SharpTS ignores a TypeScript-valid colon description after a line directive.

// @ts-expect-error: intentional assignment for the negative control
const value: number = "wrong";

Pinned TypeScript 6.0.3 reports no diagnostic for this source; SharpTS reports TS2322 because Lexer.MatchesPragma only accepts end-of-line or whitespace after the directive name. The same source with a space instead of the colon is recognized. @ts-ignore: reason has the same delimiter issue.

This differs from closed #2522, which enabled module-wide line-directive handling and unused-expectation diagnostics: the colon spelling is discarded during lexing before those policies run. Found during the PR #3487 benchmark followup; no introducing-commit claim is made.

Acceptance: recognize colon descriptions for @ts-expect-error and @ts-ignore, preserve unused-expectation TS2578, suppress only the following eligible line, and keep misleading prose/truncated/file-pragma prefixes from disabling checking. Do not replace this with @ts-nocheck or weaken the diagnostic policy.

Pinned compiler evidence covers ten accepted, unused, line-local, and misleading-prefix controls in artifacts/p3-compiler/colon-directive-oracles.json, produced by verify-colon-directives.cjs against external/typescript/lib/typescript.js version 6.0.3.