feat(cli): wire defaultProject through init and all commands

Integrates the defaultProject config field across the entire CLI
surface so that omitting `-p` now falls back to the configured default.

Init command:
- New `--default-project` flag on `lore init` (and robot-mode variant)
- InitInputs.default_project: Option<String> passed through to run_init
- Validation in run_init ensures the default matches a configured path
- Interactive mode: when multiple projects are configured, prompts
  whether to set a default and which project to use
- Robot mode: InitOutputJson now includes default_project (omitted when
  null) for downstream automation
- Autocorrect dictionary updated with `--default-project`

Command handlers applying effective_project():
- handle_issues: list filters use config default when -p omitted
- handle_mrs: same cascading resolution for MR listing
- handle_ingest: dry-run and full sync respect the default
- handle_timeline: TimelineParams.project resolved via effective_project
- handle_search: SearchCliFilters.project resolved via effective_project
- handle_generate_docs: project filter cascades
- handle_who: falls back to config.default_project when -p omitted
- handle_count: both count subcommands respect the default
- handle_discussions: discussion count filters respect the default

Robot-docs:
- init command schema updated with --default-project flag and
  response_schema showing default_project as string?
- New config_notes section documents the defaultProject field with
  type, description, and example

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/cli/mod.rs

@@ -151,6 +151,10 @@ pub enum Commands {
         /// Comma-separated project paths (required in robot mode)
         #[arg(long)]
         projects: Option<String>,
+
+        /// Default project path (used when -p is omitted)
+        #[arg(long)]
+        default_project: Option<String>,
     },
 
     #[command(hide = true)]