Implement optional discussion mode

docs/ARCHITECTURE.md

@@ -43,6 +43,9 @@ data wherever possible, not treated as an unstructured chat transcript.
 For automatic decisions, the AI Director requests only enabled automatic
 scopes and merges the response into the current project while preserving
 manual structure, arrangement, musical-parameter and production choices.
+When a Song Project uses Discuss mode, the AI Director sends the current
+project and conversation context to the provider and returns follow-up
+questions without applying a project update.
 
 ## Prompt Compiler
 

docs/DATA_MODEL.md

@@ -70,6 +70,12 @@ Auto-decision behavior
 - The AI may update production directions only when productionMode is auto.
 - Manual values remain authoritative when automatic decisions are applied.
 
+Discuss mode behavior
+- When conversationMode is discuss, the AI receives the current Song Project
+  and conversation context, then returns follow-up questions before a project
+  decision is applied.
+- A discussion response does not itself modify the Song Project.
+
 InstrumentPlacement
 - sectionId (optional)
 - startTime (optional)

docs/TASKS.md

@@ -61,7 +61,7 @@ requirement is missing and blocks implementation, record it in
 -   [x] Implement existing lyrics → correction/improvement flow.
 -   [x] Implement Auto mode for structure, arrangement, BPM/key/maqam
     and production decisions.
--   [ ] Implement optional Discuss mode.
+-   [x] Implement optional Discuss mode.
 -   [ ] Enforce user-lock/manual-value precedence over AI output.
 -   [ ] Add error, retry, cancellation and rate-limit handling.