planner/lint: classify column and table renames as app-breaking

[Kiran01bm]

Summary

A direct RENAME COLUMN / RENAME TO previously classified as metadata-only and lint passed it clean — mechanically true for PostgreSQL, but a rename cannot land atomically across running application instances: code still referencing the old name breaks the instant it commits. This PR gives renames their own typed classification so lint and plan consumers can steer to a safe sequence.

What

• New planner reason app-breaking-rename for column and table renames; the route stays native — the engine still executes the rename when asked.
• New lint warning code app-breaking-rename, derived from the classifier (single-rulebook: the linter adds severity and presentation, never a second opinion). No suggestion array — the safe sequence involves application work the engine cannot construct SQL for.
• Index renames stay metadata-only: SQL never references an index by name.
• Regression test pinning the declarative differ's behavior: a rename-shaped edit (old column gone, new column present) stays drop + add — never an inferred rename — with the drop destructive-gated (invariant RF-4).
• Reason/code rows added to the plan-report and lint-report contracts; LLD renames bullet extended.

Why

The safe path for a column rename is expand/contract — add the new column, dual-write and backfill, switch reads, then drop the old column as its own reviewed change. For a table rename, the rename must be coordinated with the application deploy that adopts the new name. Machine consumers (CI, orchestrator adapters) branch on the typed code; humans get the remedy in the report docs.

Severity is warning, not error: this repo's lint contract defines error as "the engine would refuse", and the engine executes renames (per the LLD: simple, unambiguous non-PK renames are allowed). Spirit flags column renames as an error but passes table renames because its unsafe linter is scoped to data loss — data loss is this repo's separate destructive code, so the app-compatibility warning applies to both rename kinds here.

Before / after

Before:  RENAME COLUMN / RENAME TO  -> native / metadata-only   (lint: clean)
After:   RENAME COLUMN / RENAME TO  -> native / app-breaking-rename
                                        (lint: warning app-breaking-rename)
         ALTER INDEX ... RENAME TO  -> native / metadata-only   (unchanged)

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