feat(stats): clarify indexed inventory for unsupported scopes

[SioYooo]

Summary

• Adds source-free indexed inventory counts to stats diagnostics and by-language readiness.
• Clarifies official Python v0.1 repo-shape scope versus TS/JS indexed context.
• Marks React/RN family support as unsupported and recommends exact-path find/check for PARTIAL_CONTEXT.

Validation

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo test --workspace --all-features
• python3 src/workers/python/worker.test.py
• node src/workers/typescript/worker.test.js
• npm run test:npm-wrapper
• npm_config_cache=/private/tmp/repogrammar-npm-cache npm pack --dry-run
• bash src/install/repogrammar-install.test.sh
• cargo run --quiet --bin repo-guard -- check
• cargo run --quiet --bin repo-guard -- check-diff --base origin/main --head HEAD
• git diff --check
• cmp -s AGENTS.md CLAUDE.md