chore: complete v1.0 milestone

Archive v1.0 MVP: 7 phases, 13 plans, 27/27 requirements.

- Archive roadmap to milestones/v1.0-ROADMAP.md
- Archive requirements to milestones/v1.0-REQUIREMENTS.md
- Move milestone audit into milestones/
- Create MILESTONES.md with v1.0 entry
- Evolve PROJECT.md: move shipped requirements to Validated,
  update Context with stack/LOC, log Key Decisions with outcomes
- Collapse ROADMAP.md to one-line milestone summary
- Update STATE.md to shipped status
- Back-fill stale requirements-completed frontmatter on
  02-01, 04-01, 05-01, 06-01 SUMMARY.md files

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

imptune/static/app.css

@@ -3,16 +3,42 @@
 .layout {
   display: flex;
   min-height: 100vh;
+  align-items: stretch;
 }
 
-/* Sidebar */
-.sidebar {
+.layout > * {
+  box-sizing: border-box;
+}
+
+/* Sidebar — override Pico's default nav styling (which is horizontal flex) */
+nav.sidebar {
   width: 220px;
-  flex-shrink: 0;
+  min-width: 220px;
+  max-width: 220px;
+  flex: 0 0 220px;
   border-right: 1px solid var(--pico-muted-border-color, #e0e0e0);
   padding: 1rem 0;
+  margin: 0;
   display: flex;
   flex-direction: column;
+  justify-content: flex-start;
+  align-items: stretch;
+  overflow-x: hidden;
+}
+
+nav.sidebar ul,
+nav.sidebar li {
+  margin: 0;
+  padding: 0;
+  list-style: none;
+}
+
+nav.sidebar ul {
+  display: block;
+}
+
+nav.sidebar li {
+  display: block;
 }
 
 .sidebar-brand {
@@ -22,22 +48,37 @@
   margin-bottom: 0.5rem;
 }
 
+/* Override Pico's horizontal nav ul default */
+.sidebar nav,
+.sidebar-nav {
+  display: block;
+}
+
 .sidebar-nav {
   list-style: none;
   padding: 0;
   margin: 0;
+  flex-direction: column;
 }
 
 .sidebar-nav li {
+  display: block;
   margin: 0;
+  padding: 0;
+  width: 100%;
 }
 
 .sidebar-nav a {
   display: block;
+  box-sizing: border-box;
+  width: 100%;
   padding: 0.6rem 1rem;
+  margin: 0;
   text-decoration: none;
   color: inherit;
   font-weight: 400;
+  line-height: 1.4;
+  border-left: 3px solid transparent;
 }
 
 .sidebar-nav a:hover {
@@ -47,13 +88,15 @@
 .sidebar-nav a.active {
   font-weight: 600;
   background-color: var(--pico-primary-background, rgba(0,0,0,0.08));
-  border-left: 3px solid var(--pico-primary, #1a73e8);
+  border-left-color: var(--pico-primary, #1a73e8);
 }
 
 /* Main content */
 .main-content {
-  flex: 1;
-  padding: 1.5rem;
+  flex: 1 1 auto;
+  min-width: 0;
+  padding: 1.5rem 2rem;
+  overflow-x: hidden;
   overflow-y: auto;
 }