picker-first startup with per-project sticky override (T-115)

Boot used to auto-open app.lastProject and fall back to the CWD; new
default is the welcome screen as the project picker. Sticky-open is
opt-in: a checkbox on each recent-projects row toggles a
startupSticky flag, and clide auto-opens iff exactly one row has it.
Two-or-more, or none, ⇒ picker (unambiguous user intent).

RecentProject gains the boolean (persisted in app.recentProjects);
ProjectManager exposes stickyProjectPath, openStickyOrNothing,
setStickyStartup, isStickyStartup, and preserves the flag across
reopens.

Co-Authored-By: Claude <noreply@anthropic.com>

CHANGELOG.md

@@ -18,6 +18,12 @@ heading, and (b) bumping `pubspec.yaml` `version:` in the same commit.
 
 ### Added
 
+- Startup project picker — clide now opens to the welcome screen by
+  default instead of auto-opening the last project. A per-row
+  "always open this project on launch" checkbox in welcome's RECENT
+  list sets a sticky-startup flag; if exactly one project has it,
+  that one opens directly. Two or more, or none ⇒ picker (T-115).
+
 ### Changed
 
 ### Deprecated