Clarify thread activity and lifecycle state

[VolkerChristian]

Summary

• render Last activity with the canonical primary foreground in native CodexUI and CodexWUI
• move the thread lifecycle state beside the right-aligned activity timestamp
• use canonical active blue for Running and success green for Completed
• preserve the workspace beside the thread title
• give native state labels their natural minimum width so they remain visible

Verification

• native test suite: 9/9 passed
• WebUI test suite: 76/76 passed
• Xvfb visual verification for both Running and Completed states
• git diff --check