docs: sync strategy and threat model with v0.2 state

[CoderDeltaLAN]

Summary

• update the threat model wording from stale v0.1-specific language to the current v0.2.0 release line and post-v0.2.0 main state
• update product strategy to reflect the published governance baseline and current next-direction constraints
• record the documentation sync in the unreleased changelog

Verification

• staged diff review
• stale wording guard against old v0.1 strategy/threat-model text
• secret-pattern scan on the documentation diff
• ./scripts/check.sh from a temporary development environment

Scope

Documentation only. No code, CI, release, tag, dependency, or runtime behavior changes.