Migrate mypy ignore_errors blanket to per-line directives

[fede-kamel]

Problem

`pyproject.toml` declares mypy `strict` but applies `ignore_errors = true` to 10 module groups:

• `locus.rag.*`
• `locus.memory.*`
• `locus.integrations.*`
• `locus.streaming.*`
• `locus.loop.*`
• `locus.playbooks.*`
• `locus.server.*`
• `locus.core.reducers`, `locus.core.send`
• `locus.multiagent.graph`
• `locus.hooks.builtin.*`
• `locus.reasoning.*`
• `locus.tools.context`, `locus.tools.registry`, `locus.models.registry`
• `locus.skills.*`
• `locus.a2a.*`

These modules escape static checking entirely. There are also 309 `: Any` annotations across `src/` indicating over-promised unions.

Proposed migration

For each ignored module:

1. Remove the `ignore_errors = true` block.
2. Run mypy and triage failures.
3. Replace bare `Any` with concrete types where possible (use `TypeAlias` for complex unions).
4. Add `# type: ignore[error-code]` per-line for genuine SDK-stub gaps, with a comment explaining why.
5. Cast external SDK responses explicitly at the boundary.

Acceptance

• Zero `ignore_errors` blocks in `pyproject.toml`
• `: Any` count under 100 (currently 309) in `src/`
• Every `# type: ignore` has an error code and justification comment
• mypy strict passes on full src tree

Effort

~1 week.

Source: 2026 best-in-class audit.