docs(formatter_css,fomatter_graphql,formatter_yaml): update AGENTS.md (#24821)

crates/oxc_formatter_css/AGENTS.md

@@ -10,8 +10,9 @@ Prettier compatible CSS/SCSS/Less formatter (`oxfmt`'s Tier 1 backend), using th
   - `format()`: standalone files (returns a printable `Formatted`)
   - `format_to_ir()`: embedded use via the dispatcher (e.g. css-in-js);
     tolerates `${}` placeholders and `TopLevelDeclaration`
-- The canonical reference is Prettier's `src/language-css/printer-postcss.js`
-  - port its layout decisions, do not invent new ones
+- The canonical reference is Prettier's OUTPUT (the conformance snapshots); its source is an analysis aid, not a porting target
+  - match its layout decisions, do not invent new ones
+  - never mirror its internal logic 1:1: pin behavior with fixtures, and keep implementation details of Prettier's code out of comments
   - ONE exception: never reproduce output that changes program semantics
     - See "Known divergences" section
 

crates/oxc_formatter_graphql/AGENTS.md

@@ -11,8 +11,9 @@ Prettier compatible GraphQL formatter (`oxfmt`'s Tier 1 backend), using the `oxc
   - `format_to_ir()`: embedded use via the dispatcher (e.g. graphql-in-js);
     allocates from the shared `EmbeddedContext` arena, emits no BOM / trailing newline,
     and leaves `propagate_expand()` to the parent document
-- The canonical reference is Prettier's `src/language-graphql/printer-graphql.js`
-  - port its layout decisions, do not invent new ones
+- The canonical reference is Prettier's OUTPUT (the conformance snapshots); its source is an analysis aid, not a porting target
+  - match its layout decisions, do not invent new ones
+  - never mirror its internal logic 1:1: pin behavior with fixtures, and keep implementation details of Prettier's code out of comments
 
 ### Forked parser
 

crates/oxc_formatter_yaml/AGENTS.md

@@ -8,8 +8,9 @@ Prettier compatible YAML formatter (`oxfmt`'s Tier 1 backend), using the `oxc_fo
   - See `crates/oxc_formatter_core/AGENTS.md` for the IR/pipeline details
 - Two entry points (see their docs in `src/format.rs`):
   `format()` for standalone files, `format_to_ir()` for embedded use via the dispatcher (e.g. yaml-in-markdown)
-- The canonical reference is Prettier 3.9's `src/language-yaml/printer-yaml.js` + `print/*.js`
-  - port its layout decisions — EXCEPT where they are bugs or internally inconsistent (see below)
+- The canonical reference is Prettier 3.9's OUTPUT (the conformance snapshots); its source is an analysis aid, not a porting target
+  - match its layout decisions — EXCEPT where they are bugs or internally inconsistent (see below)
+  - never mirror its internal logic 1:1: pin behavior with fixtures, and keep implementation details of Prettier's code out of comments
 
 ### Parser