Fix: Re-throw default pattern creation errors instead of swallowing (commontoolsinc#2071)

**Problem:**
Errors in DefaultPattern.create() were caught and logged but not re-thrown,
causing silent failures.

**Why this breaks mentions:**
1. linkDefaultPattern() fails (network glitch, race condition, etc.)
2. Error is swallowed → no indication to user
3. DefaultCharmList charm created successfully
4. But /defaultPattern link in space cell is missing
5. wish("#mentionable") resolves path: /defaultPattern/backlinksIndex/mentionable
6. Path resolution fails because /defaultPattern doesn't exist
7. Returns empty array instead of charm list
8. ct-code-editor receives empty mentionable list
9. [[ dropdown shows no completions

**Symptom:**
Type [[ in notes field → dropdown is empty (even though backlinksIndex has data)

**Timeline:**
- Oct 23 (947b471): linkDefaultPattern added
- Nov 6 (or earlier): Spaces created with transient link failures
- Today: Error swallowing discovered

**Fix:**
Re-throw errors to surface failures immediately. Future spaces will fail loudly
if linking doesn't work, preventing silent corruption.

**Workaround for affected spaces:**
Delete packages/toolshed/cache/memory/*.sqlite and recreate spaces.

Author: jkomoros

packages/shell/src/views/BodyView.ts

@@ -85,6 +85,8 @@ export class XBodyView extends BaseView {
       await DefaultPattern.create(this.rt.cc());
     } catch (error) {
       console.error("Could not create default pattern:", error);
+      // Re-throw to expose errors instead of swallowing them
+      throw error;
     } finally {
       this.creatingDefaultPattern = false;
       this._charms.run();