Improve partner onboarding and documentation navigation (#174)

Lead with a complete plugin quick start and add task-oriented usage, troubleshooting, customization, and contribution guides. Preserve the broader plugin framing, correct conflicting contract guidance, support Agents folder reviews, and align repository validation. Convert existing sample references to clickable links without changing knowledge rules.

Co-authored-by: Jesper Schulz-Wedde <jesper.schulzwedde@microsoft.com>
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

microsoft/skills/review/al-breaking-changes-review.md

@@ -134,7 +134,7 @@ Output conforms to the DO output contract. Every finding this skill emits MUST s
 }
 ```
 
-The empty-corpus case — BCQuality's state until breaking-changes knowledge files land — produces:
+When no applicable breaking-changes knowledge is available, the report is:
 
 ```json
 {

microsoft/skills/review/al-code-review.md

@@ -300,7 +300,9 @@ Output conforms to the DO output contract, extended with `sub-results` and `skip
 }
 ```
 
-The empty-corpus case — BCQuality's state until knowledge files land — rolls up to `no-knowledge`:
+When the selected leaves find no applicable knowledge, the result rolls up to
+`no-knowledge`. This example shows two leaf results; a full run includes every
+invoked leaf:
 
 ```json
 {

microsoft/skills/review/al-error-handling-review.md

@@ -132,7 +132,7 @@ Output conforms to the DO output contract. Every finding this skill emits MUST s
 }
 ```
 
-The empty-corpus case — BCQuality's state until error-handling knowledge files land — produces:
+When no applicable error-handling knowledge is available, the report is:
 
 ```json
 {

microsoft/skills/review/al-events-review.md

@@ -141,7 +141,7 @@ Output conforms to the DO output contract. Every finding this skill emits MUST s
 }
 ```
 
-The empty-corpus case — BCQuality's state until events knowledge files land — produces:
+When no applicable events knowledge is available, the report is:
 
 ```json
 {

microsoft/skills/review/al-performance-review.md

@@ -134,7 +134,7 @@ Output conforms to the DO output contract. Every finding this skill emits MUST s
 }
 ```
 
-The empty-corpus case — BCQuality's state until performance knowledge files land — produces:
+When no applicable performance knowledge is available, the report is:
 
 ```json
 {

microsoft/skills/review/al-security-review.md

@@ -129,7 +129,7 @@ Output conforms to the DO output contract. Every finding this skill emits MUST s
 }
 ```
 
-The empty-corpus case — BCQuality's state until security knowledge files land — produces:
+When no applicable security knowledge is available, the report is:
 
 ```json
 {