docs(changelog): distill release notes and add platform grouping

The v2.5.4 notes had grown to 97 free-form entries exposed verbatim in
the in-app update dialog. Distill them to 58 one-theme-per-line entries
capped at ~60 CJK characters with no internal terminology, and move the
writing rules into template/Changelog.md so every cycle starts from them.

Release plumbing now agrees on the --- divider: extract_update_logs.sh
stops there like updatelog.mjs, so file-only content never reaches
release bodies, while updater.mjs appends a per-tag See More link to the
update notes it generates. scripts-workflow/group_platforms.sh locks
platform entries under emoji platform headings, wired into pre-commit,
release and autobuild CI, and the changelog bump script; AGENTS.md points
agents at the template rules.

.github/workflows/autobuild.yml

@@ -35,6 +35,9 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v7
 
+      - name: Group changelog platforms
+        run: bash ./scripts-workflow/group_platforms.sh
+
       - name: Fetch UPDATE logs
         id: fetch_update_logs
         run: bash ./scripts/extract_update_logs.sh
@@ -510,6 +513,9 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v7
 
+      - name: Group changelog platforms
+        run: bash ./scripts-workflow/group_platforms.sh
+
       - name: Fetch UPDATE logs
         id: fetch_update_logs
         run: bash ./scripts/extract_update_logs.sh

.github/workflows/release.yml

@@ -92,6 +92,9 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v7
 
+      - name: Group changelog platforms
+        run: bash ./scripts-workflow/group_platforms.sh
+
       - name: Fetch UPDATE logs
         id: fetch_update_logs
         run: bash ./scripts/extract_update_logs.sh
@@ -624,6 +627,9 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v7
 
+      - name: Group changelog platforms
+        run: bash ./scripts-workflow/group_platforms.sh
+
       - name: Fetch UPDATE logs
         id: fetch_update_logs
         run: bash ./scripts/extract_update_logs.sh