docs: slim memory bank to systemPatterns and activeContext

[TKaltofen]

Summary

Slims memory-bank/ to two files so it stops drifting from the codebase.

• Fold progress.md into activeContext.md: capability inventory becomes a What Works section, known issues merge into Next Steps, achievement bullets that duplicated the Status list are dropped.
• Delete the stale May-era files: projectbrief.md, productContext.md, feature_groups.md, compute_frameworks.md, improvements/mloda_plugins_improvements.md. They predate the reader refactor (Epic: Reader refactor (ReaderRefactor) #615), unified resolution (Epic: unify FeatureGroup resolution by adapting the engine matcher (split of #722) #760), and PropertySpec hardening; their durable content lives in docs/docs/in_depth/ and README.md.
• Delete techContext.md: duplicated by the CLAUDE.md Project Practices section and pyproject.toml.
• Sync the Memory Bank table in CLAUDE.md and AGENTS.md to the two-file layout.
• Fix the stale EXPECTED_SKIP_COUNT reference (147 to 170, per tox.ini); the correct number previously lived only in the deleted techContext.md.

Test plan

• Full tox gate green locally: 7186 passed, 170 skipped, format, lint, licenses, strict mypy, bandit.
• Doc snippet tests only glob docs/, so no executable coverage is affected.