docs(skills): reorganize skill catalog into category READMEs

- Add deprecated skills README with audio-product-dsp and research-engineering
- Add productivity skills README with grill-me, handoff, writing-great-skills, and grilling
- Move forge-preferences from user-invoked to model-invoked in personal skills

common/deprecated/README.md

@@ -0,0 +1,10 @@
+# Deprecated Skills
+
+## User-invoked
+
+_None yet._
+
+## Model-invoked
+
+- [audio-product-dsp](audio-production-dispatcher/SKILL.md) — Dispatch audio product DSP hardware/software engineering requests to the best specialist workflow with measurable product-focused outputs.
+- [research-engineering](dsp-research-dispatcher/SKILL.md) — Route DSP hardware and software research-engineering requests to the best specialist workflow and return a unified, decision-ready output.

common/personal/README.md

@@ -3,11 +3,10 @@
 ## User-invoked
 
 - [conversation-summary](conversation-summary/SKILL.md) — Create compact conversation summaries for continuity.
-- [forge-preferences](forge-preferences/SKILL.md) — Apply Steve's personal or project-specific forge preferences.
 - [knowledge-gardener](knowledge-gardener/SKILL.md) — Run vault-aware semantic search, synthesis, note creation, linking, and Zettelkasten workflows.
 - [pkm-curation](pkm-curation/SKILL.md) — Curate an Obsidian-style personal knowledge vault.
 - [research-vault](research-vault/SKILL.md) — Research a topic through a one-question-at-a-time conversation and store the packet in a new Obsidian vault folder with relevant links.
 
 ## Model-invoked
 
-_None yet._
+- [forge-preferences](forge-preferences/SKILL.md) — Apply Steve's personal or project-specific forge preferences.

common/productivity/README.md

@@ -0,0 +1,11 @@
+# Productivity Skills
+
+## User-invoked
+
+- [grill-me](grill-me/SKILL.md) — A relentless interview to sharpen a plan or design.
+- [handoff](handoff/SKILL.md) — Compact the current conversation into a handoff document for another agent to pick up.
+- [writing-great-skills](writing-great-skills/SKILL.md) — Reference for writing and editing skills well — the vocabulary and principles that make a skill predictable.
+
+## Model-invoked
+
+- [grilling](grilling/SKILL.md) — Interview the user relentlessly about a plan or design.