feat: Thread optional `phase` param into `db/sessions.ts::cre… (+7 more)

- ✅ Thread optional `phase` param into `db/sessions.ts::createSession()`
- ✅ Thread optional `phase` param into `ipc/handlers.ts` sessions:create handler
- ✅ Thread optional `phase` param into `preload.ts` createSession API
- ✅ Update Plan phase system prompt to gracefully handle missing research.md
- ✅ Update Implement phase system prompt to gracefully handle missing plan.md
- ✅ Create `renderer/src/components/NewSessionModal.tsx`
- ✅ Update `App.tsx`: add modal state, split handler, add modal JSX
- ✅ Add modal CSS to `globals.css`

1 files changed, 160 insertions, 0 deletions

diff --git a/renderer/src/styles/globals.css b/renderer/src/styles/globals.css
index c463432..dc7d4a5 100644
--- a/renderer/src/styles/globals.css
+++ b/renderer/src/styles/globals.css
@@ -1711,6 +1711,166 @@ html[data-theme="light"] .settings-textarea:focus {
   margin-left: 4px;
 }
 
+/* ── New Session Modal ───────────────────────────────────────── */
+.modal-backdrop {
+  position: fixed;
+  inset: 0;
+  background: rgba(0, 0, 0, 0.55);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  z-index: 200;
+}
+
+.modal {
+  background: var(--bg-secondary);
+  border: 1px solid var(--border);
+  border-radius: 4px;
+  width: 400px;
+  display: flex;
+  flex-direction: column;
+  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.4);
+}
+
+.modal-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  padding: 12px 16px;
+  border-bottom: 1px solid var(--border);
+}
+
+.modal-title {
+  font-size: 13px;
+  font-weight: 600;
+  color: var(--text-primary);
+  text-transform: uppercase;
+  letter-spacing: 0.08em;
+}
+
+.modal-close {
+  background: transparent;
+  border: 1px solid var(--border);
+  border-radius: 2px;
+  color: var(--text-secondary);
+  font-size: 14px;
+  width: 22px;
+  height: 22px;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  transition: background 0.15s;
+}
+
+.modal-close:hover {
+  background: var(--bg-tertiary);
+  color: var(--text-primary);
+}
+
+.modal-body {
+  padding: 20px 16px 16px;
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+}
+
+.modal-prompt {
+  font-size: 12px;
+  color: var(--text-secondary);
+  text-transform: uppercase;
+  letter-spacing: 0.08em;
+}
+
+.phase-cards {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+}
+
+.phase-card {
+  display: flex;
+  flex-direction: column;
+  align-items: flex-start;
+  gap: 2px;
+  padding: 10px 12px;
+  background: var(--bg-primary);
+  border: 1px solid var(--border);
+  border-radius: 3px;
+  cursor: pointer;
+  text-align: left;
+  transition: border-color 0.15s, background 0.15s;
+  width: 100%;
+}
+
+.phase-card:hover {
+  border-color: var(--accent);
+  background: var(--bg-tertiary);
+}
+
+.phase-card.selected {
+  border-color: var(--accent);
+  background: var(--bg-tertiary);
+}
+
+.phase-card-label {
+  font-size: 12px;
+  font-weight: 600;
+  color: var(--text-primary);
+}
+
+.phase-card.selected .phase-card-label {
+  color: var(--accent);
+}
+
+.phase-card-desc {
+  font-size: 11px;
+  color: var(--text-secondary);
+}
+
+.modal-footer {
+  display: flex;
+  justify-content: flex-end;
+  gap: 8px;
+  padding: 12px 16px;
+  border-top: 1px solid var(--border);
+}
+
+.modal-btn-secondary {
+  background: transparent;
+  border: 1px solid var(--border);
+  border-radius: 2px;
+  color: var(--text-secondary);
+  font-size: 12px;
+  padding: 5px 12px;
+  cursor: pointer;
+  font-family: inherit;
+  transition: background 0.15s;
+}
+
+.modal-btn-secondary:hover {
+  background: var(--bg-tertiary);
+  color: var(--text-primary);
+}
+
+.modal-btn-primary {
+  background: var(--accent);
+  border: 1px solid var(--accent);
+  border-radius: 2px;
+  color: #fff;
+  font-size: 12px;
+  padding: 5px 12px;
+  cursor: pointer;
+  font-family: inherit;
+  font-weight: 600;
+  transition: background 0.15s;
+}
+
+.modal-btn-primary:hover {
+  background: var(--accent-hover);
+  border-color: var(--accent-hover);
+}
+
 .mcp-tools-empty {
   font-size: 11px;
   color: var(--text-secondary);