feat(q5_max): expand chord table with Greek alphabet and math symbols

Add 21 Greek letters (gamma–psi, completing the full alphabet), six
blackboard-bold number-set symbols (ℝ ℕ ℤ ℚ ℂ ℵ), and 44 new math
entries covering calculus (∫ ∂ ∇ ∑ ∏), set theory (∈ ∉ ⊂ ⊆ ∪ ∩ ∅),
logic (∀ ∃ ∧ ∨ ⟹ ⟺), geometry (∠ ⊥ ∥), and floor/ceiling brackets.

Aliases provided for longer sequences (eps→ε, prt→∂, ups→υ, omi→ο,
ang→∠).  Disambiguation notes added for mu/mute, sub/subeq, sup/supeq.

.gitignore

@@ -112,11 +112,9 @@ compile_commands.json
 via*.json
 /keyboards/**/keymaps/vial/*
 
-# AI Sessions
-.gemini_session
-.claude_session
-
 # Keep firmware file
 !keyboards/keychron/*/firmware/*.bin
+/.claude_session
 /.remember/tmp/save-session.pid
 /.direnv/CACHEDIR.TAG
+/.gemini_session