docs/build: clean up stale aliro-applet.cap references after profile split

Code review of 750f570 flagged three Important issues:
- Stale 'Output: target/aliro-applet.cap' comment in pom.xml antrun
  plugin block.
- applet/INSTALL.md referenced the old single-CAP filename in three
  places, breaking the documented gp.jar --load command.
- No safeguard or hint that -Pj3r180 and -Pj3r452 are mutually exclusive.

Updates the comments and the INSTALL.md filenames to point at
aliro-applet-j3r180.cap as the default. Adds mutual-exclusion notes
to both profile blocks.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

applet/pom.xml

@@ -88,7 +88,7 @@
                 Oracle's converter from the JC SDK pinned by JC_CLASSIC_HOME
                 (the dt-mvn.sh wrapper sets this to /app/sdks/jc305u3_kit).
 
-                Output: target/aliro-applet.cap
+                Output: target/aliro-applet-${cap.variant}.cap (j3r180 default; -Pj3r452 for AMD-H variant)
 
                 Package AID:     A0 00 00 09 09 44 54 41 4C 49 52 4F  (CSA RID + "DTALIRO")
                 Applet AIDs:
@@ -145,15 +145,18 @@
 
     <profiles>
         <profile>
+            <!-- Mutually exclusive with j3r452. Activate exactly one. -->
             <id>j3r180</id>
             <activation><activeByDefault>true</activeByDefault></activation>
             <properties>
+                <!-- cap.variant: consumed by later tasks (CI matrix, profile-conditional source roots). -->
                 <cap.variant>j3r180</cap.variant>
                 <cap.elf.aid>A0000009094454414C49524F</cap.elf.aid>
                 <cap.output.name>aliro-applet-j3r180.cap</cap.output.name>
             </properties>
         </profile>
         <profile>
+            <!-- Mutually exclusive with j3r180. Activate exactly one. -->
             <id>j3r452</id>
             <properties>
                 <cap.variant>j3r452</cap.variant>