Two inline comments. Both turn into doc-only changes — no behaviour
change — because the surfaced concerns are intentional design choices
already consistent with the rest of myschema.

diff/rename.go
  - applyColumnRenames doc-comment now states explicitly that
    `RENAME COLUMN` is MySQL 8.0+ syntax, and notes that this matches
    myschema's existing 8.0+ baseline (INVISIBLE indexes, CHECK
    constraints, etc.). Apply against an older server fails loudly
    with a syntax error rather than silently. (Copilot #1.)
  - rewriteIndexColumnRefs doc-comment now documents that
    IndexPart.Expr (functional / expression indexes) is intentionally
    NOT rewritten: rewriting embedded column references inside
    arbitrary SQL expressions requires a real parser, and getting it
    subtly wrong is more dangerous than the alternative. An
    expression index that references a renamed column will surface
    as DROP+CREATE on that one index — functionally correct, rare
    enough that the documented limitation suffices. (Copilot #2.)

AGENTS.md
  - "In scope (v1)" entry for renamed-from now spells out the MySQL
    8.0+ requirement, the full list of cross-cutting rewrites
    (index parts, FK Columns, cross-table FK RefCols, self-ref FK
    RefCols, PK constraint columns), and the documented expression-
    index limitation. Also clarifies that constraint / FK *name*
    renames are out of scope (MySQL has no in-place RENAME for
    these), distinct from constraint definition changes which
    already DROP+ADD.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>