[codex] Document Python and process provider plan

[Joncallim]

Summary

Addresses #17.

This PR adds a planning document for future Python application and native-process providers before any collector implementation begins. It defines the data DockerMap may expose, the data it must omit, fixed read-only sources, hard discovery caps, diagnostics, fixture expectations, and task-sized follow-ups.

It also aligns the roadmap, architecture, testing plan, threat model, release checklist, and docs index so the planning work is marked complete while implementation, fixtures, API checks, docs evidence, and frontend consumption remain future work.

Validation

• rg -n "PythonApplication|NativeProcess|runtime map|process|provider|redact|secret" crates packages docs tests
• path/link target inspection for changed docs
• git diff --cached --check
• npm run test:js

Review Gates

• QA: PASS after final staged-diff review
• Security: PASS after final staged-diff review
• Adversarial: PASS after final staged-diff review

Notes

This is docs/planning only. It does not add collectors, change runtime contracts, expose new data, or close the issue automatically.