fix: update skills for upstream crate relocation and e2e simplification

[slin1237]

Summary

Update all dev guide skills to reflect upstream SMG repository changes since March 3:

• Library crates moved from repo root to crates/ directory (smg#676)
• E2E parallel testing infrastructure removed, replaced with sequential execution (smg#643, smg#587)
• Multimodal crate types refactored (smg#590, smg#593)
• New subsystems added (grpc_servicer, realtime API)

Refs: smg#676, smg#643, smg#587

What changed

Crate path migration (12 recipe files):

• All library crate paths prefixed with crates/ to match new directory structure
• Affected crates: auth, data_connector, grpc_client, kv_index, mcp, mesh, multimodal, protocols, reasoning_parser, tool_parser, wasm

Cargo package name fixes (3 files):

• cargo check -p reasoning_parser → cargo check -p reasoning-parser
• cargo check -p tool_parser → cargo check -p tool-parser
• cargo test -p mcp → cargo test -p smg-mcp

Codebase map updates (skills/map/SKILL.md):

• Removed deleted MultiModalInputs type, added MediaConnector and per-model vision specs
• Added grpc_servicer package to crate table
• Added directory layout note explaining crates/ structure
• Added realtime WebSocket request flow

E2E test reference updates (skills/review-pr/SKILL.md):

• Removed @pytest.mark.thread_unsafe (parallel testing removed upstream)
• Added current markers: @pytest.mark.engine(...), @pytest.mark.gpu(count), @pytest.mark.model(...)
• Added note about sequential execution with class-scoped backends

Multimodal recipe update (skills/implement/multimodal-feature.md):

• Updated vision processor steps for per-model spec registry modules (crates/multimodal/src/registry/)

Why

The upstream SMG repository restructured all library crates into a crates/ directory and simplified the E2E test infrastructure, making the dev guide skills out of date with incorrect filesystem paths, wrong cargo package names, deleted types, and removed test markers.

How verified

• Grepped all skill files for old-style paths — zero remaining
• Cross-referenced all crates/ paths against actual upstream repo structure
• Verified cargo package names against each crate's Cargo.toml
• Confirmed thread_unsafe marker no longer exists in upstream e2e_test/

Test plan

• Verify smg:map skill shows correct crate locations
• Verify smg:implement recipes reference correct file paths
• Verify smg:review-pr file-to-section mapping matches upstream paths
• Verify smg:contribute "Where Things Live" table is accurate