Complete local operating contract positioning across docs and guidance

[codeforester]

Summary

• Replace stale product-introduction language across the ten review-identified documentation and guidance surfaces.
• Align newcomer, contributor, agent, Copilot, and standalone-library explanations with Base's local operating contract for deterministic readiness and handoff.
• Add the inventory -> prepare -> verify -> trust -> onboard -> hand off loop where the product is introduced.
• Preserve internal implementation uses of control-plane terminology while removing the retired positioning from canonical introductions.

Issue

Fixes #1757

Validation

• git diff --check
• /Users/rameshhp/.base.d/base/.venv/bin/python -m pytest -q tests/test_docs_version.py tests/test_base_cli_docs.py — 2 passed
• Targeted search confirms no workspace control plane phrase remains in the ten migrated surfaces.
• git status --short clean after commit.

Demo Impact

None. This is documentation and repository guidance only.

Notes

The migration is intentionally semantic rather than a global replacement. Internal implementation ownership language, license text, tests, and historical assessment references remain outside this issue's scope.