docs: improve TypeScript and tsconfig.json documentation

[bartlomieju]

Summary

• Add "Configuring TypeScript compiler options" and "Using tsconfig.json with Deno" sections to the fundamentals TypeScript page — so Node.js users migrating to Deno can easily find guidance on tsconfig.json compatibility
• Remove ~200 lines of duplicated content from the reference page (ts_config_migration.md), replacing with cross-links to the fundamentals page
• Fix stale --config path/to/file references, replace with link to workspaces docs
• Improve cross-linking between configuration.md, typescript.md, and ts_config_migration.md

Test plan

• Verify the new sections render correctly on the docs site
• Verify anchor links (#using-tsconfigjson-with-deno, #ts-compiler-options, etc.) resolve correctly
• Check that the fundamentals TypeScript page reads well end-to-end

🤖 Generated with Claude Code

[lunadogbot]

The new links to #using-tsconfigjson-with-deno and #ts-compiler-options resolve to headings present after this move, and the oldUrl redirects on the reference page are preserved. Approving.

• nit: the new directory tree fence in runtime/fundamentals/typescript.md is plain ```; tag it as text to match the docs code-block convention.