docs(skills): drop the duplicated ASCII field-type decision tree

`skills/objectstack-data/rules/field-types.md` carried a ~2.1 KB fenced ASCII
"Field Type Decision Tree" that re-listed the leaves of the same file's own
per-category tables. It taught nothing those tables do not already teach — each
`##` category heading answers the tree's top-level question and each row's
"When to Use" answers the leaf — and it was strictly less complete than them
(`slider` appeared in no branch). A mermaid rendering of the same tree already
ships to the same reader in the docs site.

The file is loaded whole into customer agent context on every session, so the
duplicate was billed per session, forever. Removing it frees real headroom in
the file's own density instead of taxing whichever unrelated sentence the next
author can spare.

Every table, the top-of-file blockquote and the `Common Field Configurations`
and `Incorrect vs Correct` sections are untouched; the change is a pure
deletion, no pointer line added.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019RfFHiRCSs3JXLK4cwcfox

Author: claude

skills/objectstack-data/rules/field-types.md

@@ -144,77 +144,6 @@ Stored as JSON on the parent row — no separate table / FK:
 | `tags` | Free-form tag input | — |
 | `vector` | AI/ML embeddings (semantic search, RAG) | `dimensions` (flat sibling, e.g. `1536`) |
 
-## Field Type Decision Tree
-
-```
-What kind of data?
-│
-├── Text?
-│   ├── Single line → text
-│   ├── Multiple lines → textarea
-│   ├── Formatted → richtext / markdown / html
-│   ├── Email → email
-│   ├── URL → url
-│   ├── Phone → phone
-│   ├── Credential (API key, token, DB password) → secret (encrypted at rest — NOT password)
-│   └── Code → code
-│
-├── Number?
-│   ├── Money → currency
-│   ├── Percentage → percent
-│   └── Generic → number
-│
-├── Date/Time?
-│   ├── Date only → date
-│   ├── Time only → time
-│   └── Date + Time → datetime
-│
-├── True/False?
-│   ├── Checkbox → boolean
-│   └── Switch → toggle
-│
-├── Choose from list?
-│   ├── Single choice, dropdown → select
-│   ├── Single choice, always visible → radio
-│   ├── Multiple choice, tags → multiselect
-│   └── Multiple choice, checkboxes → checkboxes
-│
-├── Reference another object?
-│   ├── Independent → lookup
-│   ├── Owned child → master_detail
-│   ├── A person (assignee, watcher) → user
-│   └── Hierarchy → tree
-│
-├── File/Media?
-│   ├── Image → image
-│   ├── Video → video
-│   ├── Audio → audio
-│   ├── User photo → avatar
-│   └── Generic file → file
-│
-├── Calculated?
-│   ├── Formula → formula
-│   ├── Roll-up → summary
-│   └── Auto-number → autonumber
-│
-├── Embedded sub-object (no separate table)?
-│   ├── Single → composite
-│   ├── Array → repeater
-│   └── Name-keyed map → record
-│
-└── Special?
-    ├── Location → location
-    ├── Address → address
-    ├── Color → color
-    ├── Rating → rating
-    ├── Signature → signature
-    ├── QR code → qrcode
-    ├── Progress → progress
-    ├── Tags → tags
-    ├── JSON data → json
-    └── AI embeddings → vector
-```
-
 ## Common Field Configurations
 
 ### Text with Max Length