[ty] Prefer innermost inline suppressions - #26940

Summary

When multiple same-line or own-line suppressions apply to the same diagnostic, prefer the innermost suppression when their ranges are nested. This keeps the closest directive marked as used and lets an outer directive continue to suppress diagnostics elsewhere in the logical statement.

For a diagnostic spanning multiple lines, a suppression on its opening line takes precedence over a separate suppression on its closing line. This is not an innermost/outermost case because neither suppression contains the other. Keeping opening-line precedence also prevents a previously used opening-line suppression from becoming unused.

The lookup is indexed by suppression target so innermost precedence does not require scanning unrelated nested suppressions for every diagnostic. The same precedence is used when checking unused-ignore-comment and blanket-ignore-comment.

Rules

Nested suppression ranges

On main, applicable suppressions are checked in source order. The outer suppression appears first, so it suppresses both diagnostics and the inner suppression is reported as unused:

# ty: ignore[unresolved-reference]  # Used for `missing` and `absent`.
values = [
    # ty: ignore[unresolved-reference]  # Unused.
    missing,
    absent,
]

With this PR, the innermost suppression wins for missing. The outer suppression remains responsible for absent, so both suppressions are used:

# ty: ignore[unresolved-reference]  # Used for `absent`.
values = [
    # ty: ignore[unresolved-reference]  # Used for `missing`.
    missing,
    absent,
]

Separate opening-line and closing-line suppressions

For a diagnostic that spans multiple lines, suppressions on its opening and closing lines can both apply even though neither suppression contains the other:

f(  # ty: ignore[missing-argument]
    g(missing))  # ty: ignore[unresolved-reference, missing-argument]

On main, the opening-line suppression wins because it appears first. This PR deliberately preserves that behavior: innermost precedence applies only when the suppression ranges are nested. The closing-line suppression still handles unresolved-reference, but its missing-argument code is unused.