feat(cli): thread list defaults to active threads only

Closes #147. Changes default behavior of `uwf thread list` to show only
active threads (idle + running). Adds `--all` flag to opt into the
previous full-list behavior. Explicit `--status` still wins over `--all`.

- cmdThreadList gains a `showAll: boolean` parameter (default false)
- CLI registers `--all` option and passes it through
- Test suite includes new `default behavior (issue #147)` describe block
  covering 9 scenarios; existing tests updated where they implicitly
  relied on the old "show everything" behavior
- README, cli-reference, and usage-reference updated to document the
  new default and the `--all` flag

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

packages/cli/src/cli.ts

@@ -233,11 +233,12 @@ function parsePaginationOptions(
 
 thread
   .command("list")
-  .description("List threads")
+  .description("List threads (defaults to active: idle + running)")
   .option(
     "--status <status>",
     "Filter by status: idle, running, completed, cancelled, active (idle+running), or comma-separated values",
   )
+  .option("--all", "Show all threads regardless of status (overrides default active-only filter)")
   .option("--after <date>", "Filter threads created after this date (ISO or relative like '7d')")
   .option("--before <date>", "Filter threads created before this date (ISO or relative like '7d')")
   .option("--skip <n>", "Skip first n threads")
@@ -245,6 +246,7 @@ thread
   .action(
     (opts: {
       status: string | undefined;
+      all: boolean | undefined;
       after: string | undefined;
       before: string | undefined;
       skip: string | undefined;
@@ -256,6 +258,7 @@ thread
         const nowMs = Date.now();
         const { afterMs, beforeMs } = parseTimeFilters(opts.after, opts.before, nowMs);
         const { skip, take } = parsePaginationOptions(opts.skip, opts.take);
+        const showAll = opts.all === true;
 
         const result = await cmdThreadList(
           storageRoot,
@@ -264,6 +267,7 @@ thread
           beforeMs,
           skip,
           take,
+          showAll,
         );
         writeOutput(result);
       });