Refactor File.Content to use discriminated union with MIME types

[kcrommett]

Summary

• Refactor File.Content to a discriminated union for type-safe text vs binary
  handling
• Add MIME detection and include it in binary responses; update SDK types and do
  cs

Changes

• Replace File.Content with a discriminated union keyed by type:
  • text: { type: "text", content, diff?, patch? }
  • binary: { type: "binary", content /* base64 */, mimeType }
• Add getMimeType(path) with common extension map and application/octet-strea m fallback
• Add isBinaryFile(path, file) using extension heuristics plus a null-byte sca
  n of the first up to 512 bytes
• Update read(path):
  • Return binary with base64 content and mimeType for detected binaries
  • Return text content; when tracked in git, compute diff and full patch
    (tries unstaged, then staged)
• Update SDK generated types to expose FileContent as a discriminated union
• Update SDK docs with usage examples for binary (data URL) vs text content

Benefits

• Strong compile-time guarantees when handling text vs binary content across ser
  ver and SDK
• Explicit mimeType metadata enables correct client-side rendering and process
  ing
• Clear API: diff/patch only on text variant; binary is base64 with metadata
• Simpler client logic using content.type discriminator

[rekram1-node]

@kmk142789 please stop reviewing prs, the review doesnt do anything since you arent a maintainer and it can lead to confusion with those trying to contribute

[rekram1-node]

@kcrommett ill peep this today thanks!