feat: auto --init flag, headless prompts, and prompt sanitizer (#1417)

* fix: Created 10 headless prompt files (5 workflows + 5 agents) in sdk/p…

- "sdk/prompts/workflows/execute-plan.md"
- "sdk/prompts/workflows/research-phase.md"
- "sdk/prompts/workflows/plan-phase.md"
- "sdk/prompts/workflows/verify-phase.md"
- "sdk/prompts/workflows/discuss-phase.md"
- "sdk/prompts/agents/gsd-executor.md"
- "sdk/prompts/agents/gsd-phase-researcher.md"
- "sdk/prompts/agents/gsd-planner.md"

GSD-Task: S01/T02

* feat: Created prompt-sanitizer.ts, wired headless prompt loading into P…

- "sdk/src/prompt-sanitizer.ts"
- "sdk/src/phase-prompt.ts"
- "sdk/src/gsd-tools.ts"
- "sdk/src/gsd-tools.test.ts"
- "sdk/src/phase-runner-types.test.ts"

GSD-Task: S01/T01

* test: Added 111 unit tests covering sanitizePrompt(), headless prompt l…

- "sdk/src/prompt-sanitizer.test.ts"
- "sdk/src/headless-prompts.test.ts"
- "sdk/src/phase-prompt.test.ts"

GSD-Task: S01/T03

* feat: Wired sdkPromptsDir preference and sanitizePrompt into InitRunner…

- "sdk/src/init-runner.ts"
- "sdk/package.json"

GSD-Task: S02/T01

* feat: add --init flag to auto command for single-command PRD-to-execution

gsd-sdk auto --init @path/to/prd.md now bootstraps the project (init)
then immediately runs the autonomous phase execution loop.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* chore: add remaining headless prompt files and templates

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* test: Extended init-runner.test.ts with 7 sdkPromptsDir preference and…

- "sdk/src/init-runner.test.ts"

GSD-Task: S02/T03

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

sdk/src/gsd-tools.test.ts

@@ -287,7 +287,7 @@ describe('GSDTools', () => {
         'init-new-project.cjs',
         `
         const args = process.argv.slice(2);
-        if (args[0] === 'init' && args[1] === 'new-project' && args.includes('--raw')) {
+        if (args[0] === 'init' && args[1] === 'new-project') {
           process.stdout.write(JSON.stringify(${JSON.stringify(mockResult)}));
         } else {
           process.stderr.write('unexpected args: ' + args.join(' '));