Fix layout-valign tests to match positional argument in minipage

Convert snapshot tests (8354, 9109) to ensureLatexFileRegexMatches
and update 7262 regex to expect [b] position. Add center alignment
test coverage.

Author: cderv

tests/docs/smoke-all/2023/11/02/7262.qmd

@@ -10,11 +10,11 @@ _quarto:
           # Verify outer figure environment wraps the layout
           - '\\begin\{figure\}[\s\S]*\\begin\{minipage\}'
           # Verify two minipages with equal width
-          - '\\begin\{minipage\}\{0\.50\\linewidth\}'
+          - '\\begin\{minipage\}\[b\]\{0\.50\\linewidth\}'
           # Verify figure[H] inside first minipage with caption and label
-          - '\\begin\{minipage\}[\s\S]*\\begin\{figure\}\[H\][\s\S]*\\caption\{\\label\{fig-example\}Figure caption\}'
+          - '\\begin\{minipage\}\[b\][\s\S]*\\begin\{figure\}\[H\][\s\S]*\\caption\{\\label\{fig-example\}Figure caption\}'
           # Verify longtable (NOT wrapped in table environment) inside second minipage
-          - '\\begin\{minipage\}\{0\.50\\linewidth\}[\s\S]*\\begin\{longtable\}'
+          - '\\begin\{minipage\}\[b\]\{0\.50\\linewidth\}[\s\S]*\\begin\{longtable\}'
           # Verify table caption with label
           - '\\caption\{\\label\{tbl-example\}Table caption\}'
           # Verify minipage ends before outer figure ends

tests/docs/smoke-all/2024/01/19/8354.qmd

@@ -1,12 +1,16 @@
 ---
 title: "Untitled"
-format: latex
+format:
+  pdf:
+    keep-tex: true
 execute:
   warning: false
 _quarto:
   tests:
-    latex:
-      ensureSnapshotMatches: true
+    pdf:
+      ensureLatexFileRegexMatches:
+        - ['\\begin\{minipage\}\[t\]\{0\.50\\linewidth\}']
+        - []
 ---
 
 ```{r}

tests/docs/smoke-all/2024/01/19/8354.tex.snapshot

@@ -0,0 +1,30 @@
+---
+title: "Untitled"
+format:
+  pdf:
+    keep-tex: true
+execute:
+  warning: false
+_quarto:
+  tests:
+    pdf:
+      ensureLatexFileRegexMatches:
+        - ['\\begin\{minipage\}\[c\]\{0\.50\\linewidth\}']
+        - []
+---
+
+```{r}
+#| label: tbl-tables
+#| tbl-cap: "Tables"
+#| tbl-subcap:
+#|   - cars
+#|   - pressure
+#| layout-ncol: 2
+#| layout-valign: center
+
+library(knitr)
+kable(head(cars))
+kable(head(pressure))
+```
+
+See @tbl-tables for examples. In particular, @tbl-tables-2.

tests/docs/smoke-all/2025/11/08/9109-center.qmd

@@ -1,12 +1,16 @@
 ---
 title: "Untitled"
-format: latex
+format:
+  pdf:
+    keep-tex: true
 execute:
   warning: false
 _quarto:
   tests:
-    latex:
-      ensureSnapshotMatches: true
+    pdf:
+      ensureLatexFileRegexMatches:
+        - ['\\begin\{minipage\}\[b\]\{0\.50\\linewidth\}']
+        - []
 ---
 
 ```{r}