[kvlonge]

Why

sqb plan prints each changed model's query diff, config diff and schema findings, but sqb plan --json left them out, so the UI and other tools could not show the same detail.

Changes

• Plan JSON gains optional query_diff, config_diff and schema_findings per changed model. The text plan reads the same diffs and only colours them, and its output is unchanged.
• A plan read through the server drops models[].query_diff and config_diff for a reader without view_sql on every current node, as it already did for Python identity_diff.
• A location reads sqb plan output up to eight times the plan size cap. A plan over the cap keeps its plan and drops the model diffs, instead of failing as too large to show. A failed plan is never read as a plan.
• No control API endpoints change; the plan document gains optional keys.

BEGIN_COMMIT_OVERRIDE
feat(plan): sqb plan --json now includes each changed model's query diff, config diff and schema findings, as the text plan prints them
END_COMMIT_OVERRIDE

Verification

• Person plan reads pass on SQLite and PostgreSQL, and assert that a viewer without view_sql gets no model diffs.
• New location plan tests cover diffs kept under the cap, dropped over it, and a failed plan.
• Plan output unit tests: 75 passed. clippy (-D warnings), rustfmt and fensu are clean.
• The touched files are identical between the original base and current main. full-verify builds and tests this on main.