feat: Add new skills and templates for domain modeling, bug diagnosis, and architectural improvement

- Introduced a human-in-the-loop script for bug diagnosis to capture user feedback.
- Created ADR and CONTEXT formats to standardize architectural decision records and domain context documentation.
- Developed a domain modeling skill to refine terminology and maintain a shared language.
- Enhanced the improve-codebase-architecture skill to provide visual reports and deepening opportunities.
- Consolidated grilling and handoff skills for better user interaction and documentation.
- Updated existing skills to improve clarity and consistency in descriptions and functionality.

README.md

@@ -113,7 +113,7 @@ For automated tests, a red-green-refactor loop is critical. This is where the ag
 
 I've built a **[`/tdd`](./skills/engineering/tdd/SKILL.md) skill** you can slot into any project. It encourages red-green-refactor and gives the agent plenty of guidance on what makes good and bad tests.
 
-For debugging, I've also built a **[`/diagnose`](./skills/engineering/diagnose/SKILL.md)** skill that wraps best debugging practices into a simple loop.
+For debugging, I've also built a **[`/diagnosing-bugs`](./skills/engineering/diagnosing-bugs/SKILL.md)** skill that wraps best debugging practices into a simple loop.
 
 ### #4: We Built A Ball Of Mud
 
@@ -142,31 +142,46 @@ Software engineering fundamentals matter more than ever. These skills are my bes
 
 ## Reference
 
+These come in two flavours. **Commands** are always user-invoked (you type `/grill-me`); their job is to orchestrate. **Skills** can be invoked by you _or_ reached for automatically by the agent when the task fits; they hold the reusable discipline. A command may invoke skills, but never another command.
+
 ### Engineering
 
 Skills I use daily for code work.
 
-- **[diagnose](./skills/engineering/diagnose/SKILL.md)** — Disciplined diagnosis loop for hard bugs and performance regressions: reproduce → minimise → hypothesise → instrument → fix → regression-test.
-- **[grill-with-docs](./skills/engineering/grill-with-docs/SKILL.md)** — Grilling session that challenges your plan against the existing domain model, sharpens terminology, and updates `CONTEXT.md` and ADRs inline.
-- **[triage](./skills/engineering/triage/SKILL.md)** — Triage issues through a state machine of triage roles.
-- **[improve-codebase-architecture](./skills/engineering/improve-codebase-architecture/SKILL.md)** — Find deepening opportunities in a codebase, informed by the domain language in `CONTEXT.md` and the decisions in `docs/adr/`.
-- **[setup-matt-pocock-skills](./skills/engineering/setup-matt-pocock-skills/SKILL.md)** — Scaffold the per-repo config (issue tracker, triage label vocabulary, domain doc layout) that the other engineering skills consume. Run once per repo before using `to-issues`, `to-prd`, `triage`, `diagnose`, `tdd`, `improve-codebase-architecture`, or `zoom-out`.
-- **[tdd](./skills/engineering/tdd/SKILL.md)** — Test-driven development with a red-green-refactor loop. Builds features or fixes bugs one vertical slice at a time.
-- **[to-issues](./skills/engineering/to-issues/SKILL.md)** — Break any plan, spec, or PRD into independently-grabbable GitHub issues using vertical slices.
-- **[to-prd](./skills/engineering/to-prd/SKILL.md)** — Turn the current conversation context into a PRD and submit it as a GitHub issue. No interview — just synthesizes what you've already discussed.
-- **[zoom-out](./skills/engineering/zoom-out/SKILL.md)** — Tell the agent to zoom out and give broader context or a higher-level perspective on an unfamiliar section of code.
+**Commands**
+
+- **[grill-with-docs](./skills/engineering/grill-with-docs/SKILL.md)** — Grilling session that also builds your project's domain model, sharpening terminology and updating `CONTEXT.md` and ADRs inline.
+- **[triage](./skills/engineering/triage/SKILL.md)** — Move issues through a state machine of triage roles.
+- **[improve-codebase-architecture](./skills/engineering/improve-codebase-architecture/SKILL.md)** — Scan a codebase for deepening opportunities, present them as a visual HTML report, then grill through whichever one you pick.
+- **[setup-matt-pocock-skills](./skills/engineering/setup-matt-pocock-skills/SKILL.md)** — Configure this repo for the engineering skills (issue tracker, triage labels, domain doc layout). Run once per repo before using the other engineering skills.
+- **[to-issues](./skills/engineering/to-issues/SKILL.md)** — Break any plan, spec, or PRD into independently-grabbable issues using vertical slices.
+- **[to-prd](./skills/engineering/to-prd/SKILL.md)** — Turn the current conversation into a PRD and publish it to the issue tracker. No interview — just synthesizes what you've already discussed.
+- **[zoom-out](./skills/engineering/zoom-out/SKILL.md)** — Ask the agent to zoom out a level and map the relevant modules and callers on an unfamiliar section of code.
 - **[prototype](./skills/engineering/prototype/SKILL.md)** — Build a throwaway prototype to flesh out a design — either a runnable terminal app for state/business-logic questions, or several radically different UI variations toggleable from one route.
 
+**Skills**
+
+- **[diagnosing-bugs](./skills/engineering/diagnosing-bugs/SKILL.md)** — Disciplined diagnosis loop for hard bugs and performance regressions: reproduce → minimise → hypothesise → instrument → fix → regression-test.
+- **[tdd](./skills/engineering/tdd/SKILL.md)** — Test-driven development with a red-green-refactor loop. Builds features or fixes bugs one vertical slice at a time.
+- **[domain-modeling](./skills/engineering/domain-modeling/SKILL.md)** — Actively build and sharpen a project's domain model — challenge terms against the glossary, stress-test with edge-case scenarios, and update `CONTEXT.md` and ADRs inline.
+- **[codebase-design](./skills/engineering/codebase-design/SKILL.md)** — Shared discipline and vocabulary for designing deep modules: a lot of behaviour behind a small interface, placed at a clean seam, testable through that interface.
+
 ### Productivity
 
 General workflow tools, not code-specific.
 
+**Commands**
+
 - **[caveman](./skills/productivity/caveman/SKILL.md)** — Ultra-compressed communication mode. Cuts token usage ~75% by dropping filler while keeping full technical accuracy.
 - **[grill-me](./skills/productivity/grill-me/SKILL.md)** — Get relentlessly interviewed about a plan or design until every branch of the decision tree is resolved.
 - **[handoff](./skills/productivity/handoff/SKILL.md)** — Compact the current conversation into a handoff document so another agent can continue the work.
 - **[teach](./skills/productivity/teach/SKILL.md)** — Teach the user a new skill or concept over multiple sessions, using the current directory as a stateful teaching workspace.
 - **[write-a-skill](./skills/productivity/write-a-skill/SKILL.md)** — Create new skills with proper structure, progressive disclosure, and bundled resources.
 
+**Skills**
+
+- **[grilling](./skills/productivity/grilling/SKILL.md)** — Interview the user relentlessly about a plan or design until every branch of the decision tree is resolved. The reusable loop behind `grill-me` and `grill-with-docs`.
+
 ### Misc
 
 Tools I keep around but rarely use.