chore: add ty as supplemental type checker

[phernandez]

Summary

• add Astral ty to the dev dependency group
• add just typecheck-ty (uv run ty check src/) so we can run ty alongside pyright
• document incremental rollout in both README.md and AGENTS.md

Verification

• just typecheck (passes)
• just typecheck-ty (currently reports diagnostics; incremental adoption path)

Notes

• this PR intentionally keeps pyright as the primary blocking type checker
• ty is introduced as a supplemental checker so we can tighten over time

[github-actions]

Claude finished @phernandez's task in 1m 33s —— View job

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PR Review: chore: add ty as supplemental type checker

• Gather context and read changed files
• Review code quality & standards
• Review testing & documentation
• Review architecture considerations
• Review security & performance
• Review compatibility
• Post final summary

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Summary

This is a clean, minimal tooling PR. It adds Astral's ty as a non-blocking supplemental type checker alongside the existing Pyright setup. The incremental adoption strategy is well-reasoned given ty's pre-release status.

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Checklist

Code Quality & Standards

• Follows Basic Memory's coding conventions in CLAUDE.md
• No commented-out code blocks
• Line length limits — N/A (no source changes)
• Python type annotations / async patterns — N/A (no source changes)

Testing & Documentation

• 100% test coverage maintained — unaffected (tooling/docs only)
• Documentation updated — README.md and AGENTS.md both updated clearly
• CLAUDE.md (AGENTS.md) updated to document the new typecheck-ty command

Basic Memory Architecture

• No database, MCP, or knowledge graph changes — N/A
• Local-first architecture unaffected

Security & Performance

• No secrets or credentials
• uv.lock includes SHA-256 hashes for all ty wheels — supply chain integrity preserved
• ty is dev-only; not present in production dependencies

Compatibility

• ty wheels are provided for win32, win_amd64, and win_arm64 in the lock file — Windows coverage confirmed
• No emoji or Unicode added to console/log output

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Observations

Minor: Version pin is a loose lower-bound on a pre-release package

# pyproject.toml:99
"ty>=0.0.18",

ty is explicitly in pre-release (0.0.x), meaning its API/behavior may change significantly between versions. A loose >= bound means fresh installs could pick up a newer version whose diagnostics differ. Since uv.lock hard-pins 0.0.18 in practice, the risk is low for team members using uv — but if someone resolves dependencies outside the lock file (e.g., in a CI matrix that upgrades lockfiles), they may get surprising results. Consider ty~=0.0.18 (compatible release) as a tighter signal of intent while still allowing patch-level updates.

This is a minor point and does not block the PR.

typecheck-ty is intentionally not in fast-check or check — confirmed appropriate given the stated incremental adoption path. The just check gate remains lint format typecheck test (pyright-only), which is correct.

No CI enforcement — also intentional per the PR description. The diagnostic-first approach before enforcing in CI is sensible for an early-stage tool.

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Verdict

Looks good to merge. The change is well-scoped, clearly documented, and doesn't affect existing type-checking gates or test coverage. The supplemental/non-blocking framing is the right call for a 0.0.x tool.