feat: add Haskell language support

[albertodvp]

Summary

Adds end-to-end Haskell support, including .hs and .lhs source detection, Cabal project detection, tree-sitter structural extraction, internal module resolution, test conventions, and analysis guidance. This enables /understand to produce useful dependency graphs for real Haskell projects instead of treating their source files as unsupported.

Linked issue(s)

No linked issue.

How I tested this

Revalidated against the current branch on 2026-08-16:

• pnpm lint
• pnpm --filter @understand-anything/core build
• pnpm --filter @understand-anything/core test — 980/980 tests passed
• Scanner suite — 42/42 tests passed
• Import-map suite — 62/62 tests passed
• Merge graph Python suite — 85/85 tests passed
• Manual smoke test against Pandoc

Pandoc smoke-test evidence:

• 2,800 files scanned, including 366 Haskell files
• Knowledge graph generated with 7,238 nodes and 8,711 relationships
• Dashboard loaded successfully and rendered the Pandoc architecture graph
• An incremental Haskell probe was detected as the 367th Haskell file
• Its function and export were extracted successfully
• Its Text.Pandoc import resolved to src/Text/Pandoc.hs

Resolved regressions

• test/Main.hs, tests/Main.hs, and their .lhs equivalents are now classified as test entry points while production Main modules remain production.
• Literate Haskell tests such as test/FooSpec.lhs now map deterministically to .lhs production candidates under test/, src/, app/, and lib/.
• End-to-end regression coverage verifies both .lhs supplemental linking and correction of inverted test/Main.hs → production edges into canonical production → test/Main.hs edges.
• Haskell registry conventions now match the deterministic merger for Spec, Test, Tests, and test-suite Main files across .hs and .lhs.

Versioning

• Version bumped from 2.9.4 to 2.10.0 in all six manifests required by CLAUDE.md.