Support juliac --trim=safe for AbsLog{2} solvers

[timholy]

• Add SparseCholesky with a concretely typed CHOLMOD workspace to bypass dynamic dispatch through task-local storage. Use it for Woodbury and LSQR, reusing solve workspaces.
• Remove boxed captures and abstract factorization storage, and use a shared row/column index type in flat_support.
• Use fixed-arity eachindex checks and direct SparseMatrixCSC construction to avoid statically unresolvable calls.

Relax the LSQR allocation ratio bound: reduced per-solve overhead exposes superlinear preconditioner fill.

Assisted-by: Claude Fable 5.1 noreply@anthropic.com

[codecov]

Codecov Report

❌ Patch coverage is 99.05213% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 98.94%. Comparing base (452d446) to head (23b551e).

Files with missing lines	Patch %	Lines
src/sparse_cholesky.jl	98.38%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #55      +/-   ##
==========================================
- Coverage   98.94%   98.94%   -0.01%     
==========================================
  Files          15       16       +1     
  Lines        3900     4060     +160     
==========================================
+ Hits         3859     4017     +158     
- Misses         41       43       +2     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.