docs: expand Chord-Unicode reference with Greek alphabet and math sections

Add Greek Alphabet table (full A–Ω), Number Sets (ℝ ℕ ℤ ℚ ℂ ℵ),
Calculus/Analysis, Set Theory, Logic, Geometry, and Floor & Ceiling
sections to match the new chord table entries.  Move pi and micro out
of Math & Science into their respective sections; add equiv and prop.
Disambiguation notes added for mu, sub, and sup.

Chord-Unicode.md

@@ -60,14 +60,109 @@ Characters are sent using the **Linux unicode input method**: `Ctrl+Shift+U`, th
 | `div` | | ÷ | Division sign |
 | `times` | `mult` | × | Multiplication sign |
 | `infty` | `inf` | ∞ | Infinity |
-| `pi` | | π | Pi |
 | `micro` | | µ | Micro sign |
-| `sigma` | | Σ | Capital sigma |
-| `delta` | | Δ | Capital delta |
-| `theta` | | θ | Theta |
-| `omega` | | Ω | Capital omega |
+| `equiv` | | ≡ | Congruent / equivalent |
+| `prop` | | ∝ | Proportional to |
+
+### Greek Alphabet
+
+| Sequence | Also accepts | Character | Name |
+|----------|-------------|-----------|------|
 | `alpha` | | α | Alpha |
 | `beta` | | β | Beta |
+| `gamma` | | γ | Gamma |
+| `delta` | | Δ | Delta (capital) |
+| `epsilon` | `eps` | ε | Epsilon |
+| `zeta` | | ζ | Zeta |
+| `eta` | | η | Eta |
+| `theta` | | θ | Theta |
+| `iota` | | ι | Iota |
+| `kappa` | | κ | Kappa |
+| `lambda` | | λ | Lambda |
+| `mu` | | μ | Mu ¹ |
+| `nu` | | ν | Nu |
+| `xi` | | ξ | Xi |
+| `omicron` | `omi` | ο | Omicron |
+| `pi` | | π | Pi |
+| `rho` | | ρ | Rho |
+| `sigma` | | Σ | Sigma (capital) |
+| `tau` | | τ | Tau |
+| `upsilon` | `ups` | υ | Upsilon |
+| `phi` | | φ | Phi |
+| `chi` | | χ | Chi |
+| `psi` | | ψ | Psi |
+| `omega` | | Ω | Omega (capital) |
+
+> ¹ `mu` triggers the 300 ms disambiguation timer because `mute` (🔇) begins with the same letters.
+
+### Number Sets
+
+| Sequence | Character | Name |
+|----------|-----------|------|
+| `real` | ℝ | Real numbers |
+| `nat` | ℕ | Natural numbers |
+| `intgr` | ℤ | Integers |
+| `rat` | ℚ | Rational numbers |
+| `cmplx` | ℂ | Complex numbers |
+| `aleph` | ℵ | Aleph |
+
+### Calculus / Analysis
+
+| Sequence | Also accepts | Character | Name |
+|----------|-------------|-----------|------|
+| `integ` | | ∫ | Integral |
+| `iint` | | ∬ | Double integral |
+| `oint` | | ∮ | Contour integral |
+| `partial` | `prt` | ∂ | Partial derivative |
+| `nabla` | | ∇ | Nabla / del |
+| `sum` | | ∑ | Summation |
+| `prod` | | ∏ | Product |
+
+### Set Theory
+
+| Sequence | Character | Name |
+|----------|-----------|------|
+| `elem` | ∈ | Element of |
+| `notin` | ∉ | Not element of |
+| `sub` | ⊂ | Subset of ¹ |
+| `subeq` | ⊆ | Subset or equal |
+| `sup` | ⊃ | Superset of ¹ |
+| `supeq` | ⊇ | Superset or equal |
+| `union` | ∪ | Union |
+| `inter` | ∩ | Intersection |
+| `empty` | ∅ | Empty set |
+
+> ¹ `sub` and `sup` trigger the 300 ms disambiguation timer because `subeq` / `supeq` begin with the same letters.
+
+### Logic
+
+| Sequence | Character | Name |
+|----------|-----------|------|
+| `forall` | ∀ | For all |
+| `exists` | ∃ | There exists |
+| `nexist` | ∄ | Does not exist |
+| `land` | ∧ | Logical and |
+| `lor` | ∨ | Logical or |
+| `xor` | ⊕ | Exclusive or |
+| `impl` | ⟹ | Implies |
+| `iff` | ⟺ | If and only if |
+
+### Geometry
+
+| Sequence | Also accepts | Character | Name |
+|----------|-------------|-----------|------|
+| `angle` | `ang` | ∠ | Angle |
+| `perp` | | ⊥ | Perpendicular |
+| `parl` | | ∥ | Parallel |
+
+### Floor & Ceiling
+
+| Sequence | Character | Name |
+|----------|-----------|------|
+| `lfl` | ⌊ | Left floor bracket |
+| `rfl` | ⌋ | Right floor bracket |
+| `lcl` | ⌈ | Left ceiling bracket |
+| `rcl` | ⌉ | Right ceiling bracket |
 
 ### Currency