docs: Fix outdated /speckit.* command references in quickstart.md

[kanfil]

Summary

Documentation in docs/quickstart.md still references the old /speckit.* command naming convention instead of the current /spec.* convention.

Details

In docs/quickstart.md:

• Line 327: /speckit.tasks should be /spec.tasks
• Line 330: /speckit.tasks should be /spec.tasks

Context

Per CHANGELOG.md v0.3.0, the command prefix was changed from /speckit.* to /spec.*:

• /speckit.specify → /spec.specify
• /speckit.plan → /spec.plan
• /speckit.tasks → /spec.tasks
• etc.

Note

The speckit.* references in tests are intentional - they test backward compatibility for existing projects that still use the old naming. These should NOT be changed.

Extensions continue to use speckit.{extension}.{command} pattern by design (e.g., /speckit.jira.specstoissues).

Proposed Fix

Update docs/quickstart.md lines 327 and 330 to use /spec.tasks instead of /speckit.tasks.