Support @deprecated marker on namespace aliases (fixes #62340)

[Prasad Navale (prasad2512)]

Fixes #62340

Problem

When an alias inside a namespace (such as export import Bar = example.Bar;) is marked with /** @deprecated */, using that type reference (e.g., let y: JSX.Bar;) does not trigger the deprecation suggestion diagnostic (TS6385: 'Bar' is deprecated.). This occurs because checkTypeReferenceOrImport retrieved the resolved symbol via getResolvedSymbolOrNil, which eagerly resolved the alias target and did not check whether intermediate alias symbols or declarations in the namespace were marked as @deprecated.

Fix

• In checkTypeReferenceOrImport, resolve the entity name of the type reference with dontResolveAlias: true.
• If the symbol is an alias, use resolveAliasWithDeprecationCheck to trace the alias chain, reporting deprecations if any alias or target declaration in the chain has the @deprecated tag (matching value reference deprecation behavior).
• Added unit test TestDeprecatedNamespaceAliasInTypeReference in tsc/internal/checker/checker_test.go verifying deprecation suggestions for direct types, namespace aliases, and re-exported deprecated types.

[Copilot]

🟡 Changes recommended

Existing deprecation suggestions can be lost, and import-type references still bypass the new alias check.

3 open issues

• Check deprecated aliases in import-type qualified references · New
• Preserve deprecation checks for symbols with merged type and value meanings · New
• Include re-exported export specifiers in deprecated alias checks · New

What changed in this PR

Addresses #62340 by checking namespace aliases for @deprecated when used as type references.

Changes:

• Adds alias-chain deprecation checks to the compiler.
• Adds a regression test covering direct types, namespace aliases, and deprecated targets.

File	Description
tsc/​internal/​checker/​checker.go	Checks alias deprecation during type-reference validation.
tsc/​internal/​checker/​checker_test.go	Tests namespace-alias deprecation suggestions.

_{Review effort: Balanced}

[Prasad Navale (prasad2512)]

Addressed review suggestions in commit f2ca475:

• Checked deprecated aliases in import-type qualified references (import('./foo').JSX.Bar).
• Preserved deprecation checks for symbols with merged type and value declarations.
• Included re-exported export specifiers in deprecated alias checks.
• Extended unit tests covering all cases in sc/internal/checker/checker_test.go.