Restore rich error message context in git error classes

The message getters for GitCommandError, GitHubCliError, TextGenerationError,
and GitManagerError in contracts were returning only this.detail, losing the
operation, command, and cwd context that the original local definitions
included. Restore the formatted messages so that logging and error reporting
surfaces full debugging context.

Author: cursoragent

packages/contracts/src/git.ts

@@ -232,7 +232,7 @@ export class GitCommandError extends Schema.TaggedErrorClass<GitCommandError>()(
   cause: Schema.optional(Schema.Defect),
 }) {
   override get message(): string {
-    return this.detail;
+    return `Git command failed in ${this.operation}: ${this.command} (${this.cwd}) - ${this.detail}`;
   }
 }
 
@@ -242,7 +242,7 @@ export class GitHubCliError extends Schema.TaggedErrorClass<GitHubCliError>()("G
   cause: Schema.optional(Schema.Defect),
 }) {
   override get message(): string {
-    return this.detail;
+    return `GitHub CLI failed in ${this.operation}: ${this.detail}`;
   }
 }
 
@@ -255,7 +255,7 @@ export class TextGenerationError extends Schema.TaggedErrorClass<TextGenerationE
   },
 ) {
   override get message(): string {
-    return this.detail;
+    return `Text generation failed in ${this.operation}: ${this.detail}`;
   }
 }
 
@@ -265,7 +265,7 @@ export class GitManagerError extends Schema.TaggedErrorClass<GitManagerError>()(
   cause: Schema.optional(Schema.Defect),
 }) {
   override get message(): string {
-    return this.detail;
+    return `Git manager failed in ${this.operation}: ${this.detail}`;
   }
 }