Prepare 0.2.0 usability release and refresh desktop demo

.github/ISSUE_TEMPLATE/bug_report.md

@@ -14,6 +14,8 @@ What did you expect, and what happened instead?
 
 Include steps, SolveCraft version/commit and relevant environment details. Prefer a small example without private design data.
 
-## Concrete visual context (when helpful)
+## Screenshots of the behavior (when observable)
 
-If a screenshot, short demo, diagram or example model view helps make the problem concrete, include it with the reproduction steps, even for kernel, geometry, assembly or backend behavior. Coding agents should run the example and capture the actual result themselves when possible, rather than asking a human for evidence they can produce. Annotate the focus when helpful. Exclude private designs and sensitive details; attach media or use an accessible link, not committed generated artifacts. Problems with no useful visual explanation do not require media.
+For observable CAD, UI or model behavior, include actual descriptive screenshots or a short recording from a small reproduction. This includes kernel, geometry, assembly and backend effects that can be shown in the app. Coding agents should run the app and capture the evidence themselves, rather than asking a human for evidence they can produce. Show the actual failure/result, preferably before and after, with brief steps, expected/actual behavior and annotations where helpful.
+
+Flowcharts and Mermaid diagrams cannot substitute for evidence of visible behavior. Use diagrams for architectural reasoning when actual screenshots cannot illustrate the point. Changes with no useful observable behavior may omit screenshot/video evidence. Exclude private designs and sensitive details; attach media or link to an accessible recording rather than committing generated review artifacts.

.github/pull_request_template.md

@@ -6,9 +6,11 @@ Describe the problem and resulting behavior. Link the issue when applicable.
 
 What did you run, and what were the results? Include expected and measured values for geometry changes.
 
-## Concrete visual context (when helpful)
+## Screenshots of the behavior (when observable)
 
-If a screenshot, short demo, diagram or before/after model view helps explain what this change means, include it alongside the prose. This includes kernel, geometry, assembly and backend changes, not only UI work. Coding agents should run the example and capture the actual reproduction/result themselves, adding brief steps and annotations where helpful. Use a public-safe example; exclude private designs and sensitive details, and attach media rather than committing generated review artifacts. Changes with no useful visual explanation can omit this section.
+For observable CAD, UI or model behavior, include actual descriptive screenshots or a short recording from a small reproduction. This includes kernel, geometry, assembly and backend effects that can be shown in the app. Coding agents should run the app and capture the evidence themselves, rather than asking a human for evidence they can produce. Show the actual failure/result, preferably before and after, with brief steps, expected/actual behavior and annotations where helpful.
+
+Flowcharts and Mermaid diagrams cannot substitute for evidence of visible behavior. Use diagrams for architectural reasoning when actual screenshots cannot illustrate the point. Changes with no useful observable behavior may omit screenshot/video evidence. Exclude private designs and sensitive details; attach media or link to an accessible recording rather than committing generated review artifacts.
 
 ## Integration status
 

.github/workflows/packaging-lint.yml

@@ -28,13 +28,15 @@ jobs:
       - name: Install tools
         run: |
           sudo apt-get update
-          sudo apt-get install -y --no-install-recommends shellcheck desktop-file-utils appstream libxml2-utils python3-yaml
+          sudo apt-get install -y --no-install-recommends shellcheck desktop-file-utils appstream libxml2-utils python3-yaml jq
           curl -fsSL "https://github.com/rhysd/actionlint/releases/download/v${ACTIONLINT_VERSION}/actionlint_${ACTIONLINT_VERSION}_linux_amd64.tar.gz" \
             | tar -xz -C "$RUNNER_TEMP" actionlint
       - name: actionlint
         run: '"$RUNNER_TEMP/actionlint" -color'
       - name: shellcheck
         run: shellcheck packaging/*.sh packaging/*/*.sh packaging/linux/AppRun
+      - name: Nightly release selection regression
+        run: python3 packaging/tests/nightly_test.py
       - name: PowerShell
         shell: pwsh
         run: |