Consolidate duplicate patterns and simplify codebase (#1317)

* refactor(shared): unify binary downloader and session path storage

- Create binary-downloader.ts for common download/extract logic
- Create session-injected-paths.ts for unified path tracking
- Refactor comment-checker, ast-grep, grep downloaders to use shared util
- Consolidate directory injector types into shared module

* feat(shared): implement unified model resolution pipeline

- Create ModelResolutionPipeline for centralized model selection
- Refactor model-resolver to use pipeline
- Update delegate-task and config-handler to use unified logic
- Ensure consistent model resolution across all agent types

* refactor(agents): simplify agent utils and metadata management

- Extract helper functions for config merging and env context
- Register prompt metadata for all agents
- Simplify agent variant detection logic

* cleanup: inline utilities and remove unused exports

- Remove case-insensitive.ts (inline with native JS)
- Simplify opencode-version helpers
- Remove unused getModelLimit, createCompactionContextInjector exports
- Inline transcript entry creation in claude-code-hooks
- Update tests accordingly

---------

Co-authored-by: justsisyphus <justsisyphus@users.noreply.github.com>

src/shared/opencode-version.ts

@@ -37,13 +37,6 @@ export function compareVersions(a: string, b: string): -1 | 0 | 1 {
   return 0
 }
 
-export function isVersionGte(a: string, b: string): boolean {
-  return compareVersions(a, b) >= 0
-}
-
-export function isVersionLt(a: string, b: string): boolean {
-  return compareVersions(a, b) < 0
-}
 
 export function getOpenCodeVersion(): string | null {
   if (cachedVersion !== NOT_CACHED) {
@@ -69,7 +62,7 @@ export function getOpenCodeVersion(): string | null {
 export function isOpenCodeVersionAtLeast(version: string): boolean {
   const current = getOpenCodeVersion()
   if (!current) return true
-  return isVersionGte(current, version)
+  return compareVersions(current, version) >= 0
 }
 
 export function resetVersionCache(): void {