docs: explain the P2P diagnostic workflow

Guide users through Diagnostic summary, Diag logging, transfer progress,
symptom checks, and evidence collection from both devices. Link the guide
from the P2P, troubleshooting, reporting, and documentation entry points.
Keep transport compatibility and observation limits explicit.

Validated with the troubleshooting documentation Inspector, 145 local
references, 34 heading anchors, and current English UI labels. Runtime
source and translations are unchanged.

docs/to_issue_reporting.md

@@ -11,6 +11,7 @@ If a maintainer requests additional evidence, follow the relevant procedure belo
 | Database integrity, current conflicts, or differences between sources | [Integrity report](#integrity-report) |
 | Local revision and Chunk usage                                        | [Usage report](#usage-report)         |
 | More information about a path pseudonym in an existing report         | [File follow-up](#file-follow-up)     |
+| P2P discovery, authentication, or transfer activity | [P2P summary and logs](tips/p2p-diagnostics.md#collect-a-report) |
 
 Maintainers can link directly to each procedure and adapt the [example requests](#requesting-diagnostics).