Move prompts into embedded Markdown assets

docs/architecture.md

@@ -136,6 +136,14 @@ internal/validators/
   registry.go
   chains.go
 
+internal/prompts/
+  registry.go
+  render.go
+  assets/
+    shared/
+    modules/
+    validators/
+
 internal/framework/llm/
   openai_compatible_client.go
   scheduler.go
@@ -312,6 +320,43 @@ Prompt guardrail semantics are consistent across modules and validators:
 
 Generated transcript descriptions remain deferred and are not implemented in the current runtime.
 
+## Implemented embedded prompt assets
+Prompt assets are now built-in embedded Markdown files under `internal/prompts/assets`:
+- `assets/modules/*` for production module proposal prompts;
+- `assets/validators/*` for LLM-backed validator prompts;
+- `assets/shared/prompt_hardening.md` for shared prompt-injection hardening text.
+
+Prompt source behavior:
+- built-in embedded prompts are the only supported source in current runtime;
+- filesystem prompt overrides and prompt-source selection flags are not implemented.
+
+`internal/prompts` registry responsibilities:
+- register stable prompt IDs;
+- register prompt version and source metadata;
+- load embedded assets;
+- compute deterministic SHA-256 prompt source hashes;
+- render system/user prompts with `text/template` using missing-key errors.
+
+Prompt metadata fields:
+- `prompt_id`
+- `prompt_version`
+- `prompt_source` (`builtin`)
+- `embedded_path`
+- `sha256`
+
+Prompt rendering flow:
+- module proposal builders construct typed template data (section JSON, glossary JSON, transcript-description block) and render via `internal/prompts`;
+- validator prompt builders construct typed template data (validation payload JSON, transcript-description block) and render via `internal/prompts`.
+
+Shared prompt hardening:
+- the same centralized hardening fragment is included in every proposal and LLM-validator prompt;
+- hardening text enforces untrusted transcript handling, no instruction-following from transcript content, and no invented facts/corrections.
+
+Prompt metadata diagnostics flow:
+- proposal-generation diagnostics request metadata includes prompt metadata;
+- LLM-validator diagnostics request metadata includes prompt metadata;
+- detailed prompt metadata is diagnostics-scoped today and is not yet expanded into broad report-level prompt registries.
+
 ## Implemented structured LLM infrastructure
 `internal/framework/contracts` now defines a typed structured-completion contract:
 - `StructuredLLMClient.CompleteStructured(ctx, req, out)`