docs: fix missing_docs and invalid-link errors (fix docs CI)

docs/src/api.md

@@ -6,3 +6,16 @@
 getstructure
 sparsestructure
 ```
+
+## Extension Point Functions
+
+These functions are extension points that package extensions add methods to.
+They return `nothing` unless the corresponding optional package is loaded.
+
+```@docs
+SparseMatrixIdentification.try_special_matrices
+SparseMatrixIdentification.try_toeplitz
+SparseMatrixIdentification.try_banded
+SparseMatrixIdentification.try_blockbanded
+SparseMatrixIdentification.try_almostbanded
+```

src/SparseMatrixIdentification.jl

@@ -454,7 +454,7 @@ corresponding package is loaded. Load the relevant package to enable detection:
 # Returns
 One of the following matrix types based on detected structure:
 - `Hilbert`: If A[i,j] = 1/(i+j-1) (requires SpecialMatrices)
-- `Strang`: If the matrix is tridiagonal Toeplitz with pattern [2, -1, -1] (requires SpecialMatrices)
+- `Strang`: If the matrix is tridiagonal Toeplitz with pattern `[2, -1, -1]` (requires SpecialMatrices)
 - `Vandermonde`: If columns are powers of a base vector (requires SpecialMatrices)
 - `Cauchy`: If A[i,j] = 1/(x[i] + y[j]) (requires SpecialMatrices)
 - `Toeplitz`: If the matrix has constant diagonals (requires ToeplitzMatrices)