feat: add checkpoint context types and fix state machine transitions

Add structured CheckpointContext with failureKind and touchSet violation
metadata to replace error-string parsing. Add completed->failed and
failed->running to VALID_JOB_TRANSITIONS to support touchSet violation
detection and agent relaunch flows.

Closes #61

Author: nigel-dev

src/lib/plan-types.ts

@@ -10,6 +10,15 @@ export type PlanStatus =
 
 export type CheckpointType = 'pre_merge' | 'on_error' | 'pre_pr';
 
+export type FailureKind = 'touchset' | 'merge_conflict' | 'test_failure' | 'job_failed';
+
+export interface CheckpointContext {
+  jobName: string;
+  failureKind: FailureKind;
+  touchSetViolations?: string[];
+  touchSetPatterns?: string[];
+}
+
 export type JobStatus =
   | 'queued'
   | 'waiting_deps'
@@ -39,6 +48,7 @@ export interface PlanSpec {
   completedAt?: string;
   prUrl?: string;
   checkpoint?: CheckpointType | null;
+  checkpointContext?: CheckpointContext | null;
 }
 
 export interface JobSpec {
@@ -76,8 +86,8 @@ export const VALID_JOB_TRANSITIONS: Record<JobStatus, JobStatus[]> = {
   queued: ['waiting_deps', 'running', 'stopped', 'canceled'],
   waiting_deps: ['running', 'stopped', 'canceled'],
   running: ['completed', 'failed', 'stopped', 'canceled'],
-  completed: ['ready_to_merge', 'stopped', 'canceled'],
-  failed: ['ready_to_merge', 'stopped', 'canceled'],
+  completed: ['ready_to_merge', 'failed', 'stopped', 'canceled'],
+  failed: ['ready_to_merge', 'running', 'stopped', 'canceled'],
   ready_to_merge: ['merging', 'needs_rebase', 'stopped', 'canceled'],
   merging: ['merged', 'conflict', 'stopped', 'canceled'],
   merged: ['needs_rebase'],

src/lib/schemas.ts

@@ -72,6 +72,15 @@ export const JobSpecSchema = z.object({
   mode: z.enum(['vanilla', 'plan', 'ralph', 'ulw']).optional(),
 });
 
+export const FailureKindSchema = z.enum(['touchset', 'merge_conflict', 'test_failure', 'job_failed']);
+
+export const CheckpointContextSchema = z.object({
+  jobName: z.string(),
+  failureKind: FailureKindSchema,
+  touchSetViolations: z.array(z.string()).optional(),
+  touchSetPatterns: z.array(z.string()).optional(),
+});
+
 export const PlanSpecSchema = z.object({
   id: z.string(),
   name: z.string(),
@@ -86,6 +95,7 @@ export const PlanSpecSchema = z.object({
   completedAt: z.string().optional(),
   prUrl: z.string().optional(),
   checkpoint: CheckpointTypeSchema.nullable().optional(),
+  checkpointContext: CheckpointContextSchema.nullable().optional(),
   ghAuthenticated: z.boolean().optional(),
 });