docs(skillbook): convert format decision tree to Mermaid diagram

Convert text-based decision tree to Mermaid flowchart for clarity:
- Visual flowchart with decision nodes
- Clear YES/NO paths to Format A or Format B
- Terminal node for file creation

Added to:
- src/claude/skillbook.md
- templates/agents/skillbook.shared.md
- Generated platform files (copilot-cli, vscode)

Created memory file:
- skill-format-selection-decision-tree.md
- Added to skills-documentation-index.md

Validation: 30 domains, 195 indexed files, PASSED

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: rjmurillo-bot

.serena/memories/skill-format-selection-decision-tree.md

@@ -0,0 +1,54 @@
+# Skill Format Selection Decision Tree
+
+**Statement**: Use decision tree to select Format A (standalone) or Format B (bundled) for new skills.
+
+**Context**: When creating new skill files in `.serena/memories/`
+
+**Atomicity**: 95%
+
+**Impact**: 8/10
+
+## Decision Tree (Mermaid)
+
+```mermaid
+flowchart TD
+    START([New Skill]) --> Q1{CRITICAL or<br/>BLOCKING P0?}
+    Q1 -->|YES| A1[Format A<br/>Standalone]
+    Q1 -->|NO| Q2{2+ related skills<br/>same workflow?}
+    Q2 -->|YES| B1[Format B<br/>Bundled]
+    Q2 -->|NO| Q3{Referenced by<br/>other skills?}
+    Q3 -->|YES| A2[Format A<br/>Standalone]
+    Q3 -->|NO| EITHER[Either Format<br/>Acceptable]
+
+    A1 --> DONE([Create File])
+    A2 --> DONE
+    B1 --> DONE
+    EITHER --> DONE
+```
+
+## Decision Rules
+
+| Question | YES | NO |
+|----------|-----|-----|
+| CRITICAL/BLOCKING (P0)? | Format A | Continue |
+| 2+ related skills same workflow? | Format B | Continue |
+| Referenced by other skills? | Format A | Either |
+
+## Format Definitions
+
+**Format A (Standalone)**: Full skill structure with Statement, Context, Evidence, Pattern, Anti-Pattern, Related sections. One skill per file.
+
+**Format B (Bundled)**: Multiple related skills in one file. Each skill has Statement, Atomicity, code example. Grouped by workflow.
+
+## Examples
+
+| Skill Type | Format | Example File |
+|------------|--------|--------------|
+| Session initialization (P0) | A | `session-init-serena.md` |
+| PR acknowledgment workflow (4 skills) | B | `pr-review-acknowledgment.md` |
+| GitHub CLI API patterns (4 skills) | B | `github-cli-api-patterns.md` |
+| Pester test isolation (standalone) | A | `pester-test-isolation.md` |
+
+## Evidence
+
+Derived from migration of 194 skill files during ADR-017 implementation (Session 57).

.serena/memories/skills-documentation-index.md

@@ -12,6 +12,7 @@
 | fallback tool call graceful degradation mcp serena | documentation-fallback-pattern |
 | user-facing content internal PR issue session exclude | documentation-user-facing |
 | self-contained artifact handoff agent amnesia autonomous | documentation-self-contained |
+| skill format standalone bundled decision tree mermaid P0 | skill-format-selection-decision-tree |
 
 ## Domain Statistics
 

src/claude/skillbook.md

@@ -244,18 +244,20 @@ Use for multiple related skills that share a workflow context.
 
 ### Format Selection Decision Tree
 
-```text
-1. Is this a CRITICAL/BLOCKING skill (P0)?
-   YES → Format A (standalone, full detail)
-   NO  → Continue
-
-2. Are there 2+ related skills in the same workflow?
-   YES → Format B (bundled in one file)
-   NO  → Format A (standalone)
-
-3. Is the skill referenced by other skills?
-   YES → Format A (standalone for linkability)
-   NO  → Either format acceptable
+```mermaid
+flowchart TD
+    START([New Skill]) --> Q1{CRITICAL or<br/>BLOCKING P0?}
+    Q1 -->|YES| A1[Format A<br/>Standalone]
+    Q1 -->|NO| Q2{2+ related skills<br/>same workflow?}
+    Q2 -->|YES| B1[Format B<br/>Bundled]
+    Q2 -->|NO| Q3{Referenced by<br/>other skills?}
+    Q3 -->|YES| A2[Format A<br/>Standalone]
+    Q3 -->|NO| EITHER[Either Format<br/>Acceptable]
+
+    A1 --> DONE([Create File])
+    A2 --> DONE
+    B1 --> DONE
+    EITHER --> DONE
 ```
 
 ### Skill Categories

src/copilot-cli/skillbook.agent.md

@@ -206,18 +206,20 @@ Use for multiple related skills that share a workflow context.
 
 ### Format Selection Decision Tree
 
-```text
-1. Is this a CRITICAL/BLOCKING skill (P0)?
-   YES → Format A (standalone, full detail)
-   NO  → Continue
-
-2. Are there 2+ related skills in the same workflow?
-   YES → Format B (bundled in one file)
-   NO  → Format A (standalone)
-
-3. Is the skill referenced by other skills?
-   YES → Format A (standalone for linkability)
-   NO  → Either format acceptable
+```mermaid
+flowchart TD
+    START([New Skill]) --> Q1{CRITICAL or<br/>BLOCKING P0?}
+    Q1 -->|YES| A1[Format A<br/>Standalone]
+    Q1 -->|NO| Q2{2+ related skills<br/>same workflow?}
+    Q2 -->|YES| B1[Format B<br/>Bundled]
+    Q2 -->|NO| Q3{Referenced by<br/>other skills?}
+    Q3 -->|YES| A2[Format A<br/>Standalone]
+    Q3 -->|NO| EITHER[Either Format<br/>Acceptable]
+
+    A1 --> DONE([Create File])
+    A2 --> DONE
+    B1 --> DONE
+    EITHER --> DONE
 ```
 
 ### Skill Categories

src/vs-code-agents/skillbook.agent.md

@@ -206,18 +206,20 @@ Use for multiple related skills that share a workflow context.
 
 ### Format Selection Decision Tree
 
-```text
-1. Is this a CRITICAL/BLOCKING skill (P0)?
-   YES → Format A (standalone, full detail)
-   NO  → Continue
-
-2. Are there 2+ related skills in the same workflow?
-   YES → Format B (bundled in one file)
-   NO  → Format A (standalone)
-
-3. Is the skill referenced by other skills?
-   YES → Format A (standalone for linkability)
-   NO  → Either format acceptable
+```mermaid
+flowchart TD
+    START([New Skill]) --> Q1{CRITICAL or<br/>BLOCKING P0?}
+    Q1 -->|YES| A1[Format A<br/>Standalone]
+    Q1 -->|NO| Q2{2+ related skills<br/>same workflow?}
+    Q2 -->|YES| B1[Format B<br/>Bundled]
+    Q2 -->|NO| Q3{Referenced by<br/>other skills?}
+    Q3 -->|YES| A2[Format A<br/>Standalone]
+    Q3 -->|NO| EITHER[Either Format<br/>Acceptable]
+
+    A1 --> DONE([Create File])
+    A2 --> DONE
+    B1 --> DONE
+    EITHER --> DONE
 ```
 
 ### Skill Categories

templates/agents/skillbook.shared.md

@@ -206,18 +206,20 @@ Use for multiple related skills that share a workflow context.
 
 ### Format Selection Decision Tree
 
-```text
-1. Is this a CRITICAL/BLOCKING skill (P0)?
-   YES → Format A (standalone, full detail)
-   NO  → Continue
-
-2. Are there 2+ related skills in the same workflow?
-   YES → Format B (bundled in one file)
-   NO  → Format A (standalone)
-
-3. Is the skill referenced by other skills?
-   YES → Format A (standalone for linkability)
-   NO  → Either format acceptable
+```mermaid
+flowchart TD
+    START([New Skill]) --> Q1{CRITICAL or<br/>BLOCKING P0?}
+    Q1 -->|YES| A1[Format A<br/>Standalone]
+    Q1 -->|NO| Q2{2+ related skills<br/>same workflow?}
+    Q2 -->|YES| B1[Format B<br/>Bundled]
+    Q2 -->|NO| Q3{Referenced by<br/>other skills?}
+    Q3 -->|YES| A2[Format A<br/>Standalone]
+    Q3 -->|NO| EITHER[Either Format<br/>Acceptable]
+
+    A1 --> DONE([Create File])
+    A2 --> DONE
+    B1 --> DONE
+    EITHER --> DONE
 ```
 
 ### Skill Categories