fix(placeholders): remove redundant MatchString guard and update all rule READMEs

- Drop the MatchString pre-check before ReplaceAllLiteralString in MaskBodyTokens
  and stripBodyTokens: ReplaceAllLiteralString returns the original string when
  the regex finds no match, so MatchString + ReplaceAll was scanning the regex
  engine twice per matching node. ContainsBodyToken correctly keeps the double
  guard since it needs a boolean return without side effects.
- Update Useful tokens line in MDS003, MDS004, MDS018, MDS023, MDS024, and MDS027
  per-rule READMEs to list apm-input-token alongside the existing tokens (the
  global placeholder-grammar.md table was already updated; these were overlooked).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015Cua8NLiPy6fhj58LvUWf1

Author: claude

internal/placeholders/placeholders.go

@@ -110,7 +110,7 @@ func MaskBodyTokens(text string, tokens []string) string {
 				return neutralText[PlaceholderSection]
 			}
 		case APMInputToken:
-			if strings.Contains(text, apmInputPrefix) && apmInputRe.MatchString(text) {
+			if strings.Contains(text, apmInputPrefix) {
 				text = apmInputRe.ReplaceAllLiteralString(text, neutralText[APMInputToken])
 			}
 		}
@@ -147,7 +147,7 @@ func stripBodyTokens(text string, tokens []string) string {
 				return ""
 			}
 		case APMInputToken:
-			if strings.Contains(text, apmInputPrefix) && apmInputRe.MatchString(text) {
+			if strings.Contains(text, apmInputPrefix) {
 				text = apmInputRe.ReplaceAllLiteralString(text, "")
 			}
 		}

internal/rules/MDS003-heading-increment/README.md

@@ -47,7 +47,7 @@ Heading levels should increment by one. No jumping from `#` to `###`.
 | -------------- | ---- | ------- | -------------------------------------------------------------------------------------------------------------------------- |
 | `placeholders` | list | `[]`    | Placeholder tokens to treat as opaque; see [placeholder grammar](../../../docs/background/concepts/placeholder-grammar.md) |
 
-Useful tokens: `heading-question`, `placeholder-section`, `var-token`.
+Useful tokens: `heading-question`, `placeholder-section`, `var-token`, `apm-input-token`.
 
 ## Config
 

internal/rules/MDS004-first-line-heading/README.md

@@ -36,7 +36,7 @@ First line of the file should be a heading.
 | `level`        | int  | 1       | Required heading level for the first line                                                                                  |
 | `placeholders` | list | `[]`    | Placeholder tokens to treat as opaque; see [placeholder grammar](../../../docs/background/concepts/placeholder-grammar.md) |
 
-Useful tokens: `heading-question`, `var-token`, `placeholder-section`.
+Useful tokens: `heading-question`, `var-token`, `placeholder-section`, `apm-input-token`.
 
 ## Config
 

internal/rules/MDS018-no-emphasis-as-heading/README.md

@@ -39,7 +39,7 @@ Don't use bold or emphasis on a standalone line as a heading substitute.
 | -------------- | ---- | ------- | -------------------------------------------------------------------------------------------------------------------------- |
 | `placeholders` | list | `[]`    | Placeholder tokens to treat as opaque; see [placeholder grammar](../../../docs/background/concepts/placeholder-grammar.md) |
 
-Useful tokens: `var-token`, `heading-question`, `placeholder-section`.
+Useful tokens: `var-token`, `heading-question`, `placeholder-section`, `apm-input-token`.
 
 ## Config
 

internal/rules/MDS023-paragraph-readability/README.md

@@ -25,7 +25,7 @@ Paragraph readability index must not exceed a threshold.
 | `min-words`    | int   | 20      | Minimum word count to check a paragraph                                                                                    |
 | `placeholders` | list  | `[]`    | Placeholder tokens to treat as opaque; see [placeholder grammar](../../../docs/background/concepts/placeholder-grammar.md) |
 
-Useful tokens: `var-token`, `heading-question`, `placeholder-section`.
+Useful tokens: `var-token`, `heading-question`, `placeholder-section`, `apm-input-token`.
 
 Paragraphs with fewer words than `min-words` are skipped.
 Markdown tables and code blocks are skipped.

internal/rules/MDS024-paragraph-structure/README.md

@@ -25,7 +25,7 @@ Paragraphs must not exceed sentence and word limits.
 | `max-words-per-sentence` | int  | 40      | Maximum words per sentence                                                                                                 |
 | `placeholders`           | list | `[]`    | Placeholder tokens to treat as opaque; see [placeholder grammar](../../../docs/background/concepts/placeholder-grammar.md) |
 
-Useful tokens: `var-token`, `heading-question`, `placeholder-section`.
+Useful tokens: `var-token`, `heading-question`, `placeholder-section`, `apm-input-token`.
 
 Markdown tables and code blocks are skipped.
 

internal/rules/MDS027-cross-file-reference-integrity/README.md

@@ -44,7 +44,7 @@ Links to local files and heading anchors must resolve.
 | `wikilinks`      | bool   | `false`      | Validate Obsidian-style `[[Page]]`, `[[Page#anchor]]`, `[[Page\|alias]]`, and `![[file.png]]` targets against the workspace. |
 | `wikilink-style` | string | `"obsidian"` | Resolution style for wikilinks. Only `obsidian` ships today; other values are rejected at config load.                       |
 
-Useful tokens: `var-token`, `heading-question`, `placeholder-section`.
+Useful tokens: `var-token`, `heading-question`, `placeholder-section`, `apm-input-token`.
 
 With `strict: false`, only Markdown targets (`.md`, `.markdown`)
 are checked (except images — see `links.validate-images`).