docs(data-modeling): drop the flowchart edge that routed secret values to password

The Text? branch of the field-type decision-tree flowchart had
`TEXT -->|Secret value| T8[password]`, contradicting the same page's
quick-reference table (password: "masked on read; stored plaintext at
rest ... prefer secret for real credentials"), ADR-0100, and the
published skill rule — all of which say a secret value belongs in
`secret`.

The flowchart already has a correct edge for this
(`STRUCT -->|Sensitive secret value| S5[secret]`), so rather than add a
second edge into the same `secret` node (which would leave two
differently-labeled paths converging on one answer), the wrong edge is
dropped outright and its now-unused `T8`/`password` style line removed.
The `password` type and its table row are untouched — it's a real,
supported type, just not one the flowchart should route credentials to.

Full flowchart audited edge-by-edge against the quick-reference table;
no other edge disagrees with its table row.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012GKcPZbMoGq7WPzKLfRBTU

Author: claude

content/docs/data-modeling/field-type-decision-tree.mdx

@@ -33,7 +33,6 @@ flowchart TD
     TEXT -->|Email address| T5[email]
     TEXT -->|Website URL| T6[url]
     TEXT -->|Phone number| T7[phone]
-    TEXT -->|Secret value| T8[password]
 
     %% Number branch
     NUM -->|Any number| N1[number]
@@ -88,7 +87,6 @@ flowchart TD
     style T5 fill:#059669,color:#fff
     style T6 fill:#059669,color:#fff
     style T7 fill:#059669,color:#fff
-    style T8 fill:#059669,color:#fff
     style N1 fill:#d97706,color:#fff
     style N3 fill:#d97706,color:#fff
     style N4 fill:#d97706,color:#fff