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/agent-variant.ts

@@ -1,5 +1,4 @@
 import type { OhMyOpenCodeConfig } from "../config"
-import { findCaseInsensitive } from "./case-insensitive"
 import { AGENT_MODEL_REQUIREMENTS, CATEGORY_MODEL_REQUIREMENTS } from "./model-requirements"
 
 export function resolveAgentVariant(
@@ -13,7 +12,10 @@ export function resolveAgentVariant(
   const agentOverrides = config.agents as
     | Record<string, { variant?: string; category?: string }>
     | undefined
-  const agentOverride = agentOverrides ? findCaseInsensitive(agentOverrides, agentName) : undefined
+  const agentOverride = agentOverrides
+    ? agentOverrides[agentName]
+      ?? Object.entries(agentOverrides).find(([key]) => key.toLowerCase() === agentName.toLowerCase())?.[1]
+    : undefined
   if (!agentOverride) {
     return undefined
   }
@@ -43,7 +45,10 @@ export function resolveVariantForModel(
   const agentOverrides = config.agents as
     | Record<string, { category?: string }>
     | undefined
-  const agentOverride = agentOverrides ? findCaseInsensitive(agentOverrides, agentName) : undefined
+  const agentOverride = agentOverrides
+    ? agentOverrides[agentName]
+      ?? Object.entries(agentOverrides).find(([key]) => key.toLowerCase() === agentName.toLowerCase())?.[1]
+    : undefined
   const categoryName = agentOverride?.category
   if (categoryName) {
     const categoryRequirement = CATEGORY_MODEL_REQUIREMENTS[categoryName]