[GaganSD]

Summary

• Show context percentage and MCP count on the focused composer top edge without duplicate context or cost metadata.
• Match metadata separators to surrounding theme tones.
• Remove Slate update checking and header hairlines; retain native Pi update notices.
• Use matching 4×2 geometry for original and minimal header marks.
• Add /logo to toggle styles directly, plus /logo original and /logo minimal with argument completions.

Validation

• All package tests pass, including 620 Slate tests.
• All package typechecks and Slate lint pass.
• Added toggle and argument-completion regression coverage.
• Repository-wide lint has pre-existing errors outside this PR.