readMetaFromMeta narrows the opaque persisted meta boundary, so beyond
shape it now rejects replayed JSON that is well-typed but semantically
invalid: line numbers must be 1-based integers, totalLines a non-negative
integer, and line numbers must strictly increase without exceeding
totalLines. Any violation declines to the generic fallback.
Sync the public ToolResultView contract across the core/tools and
tool-fs READMEs and docs/core-data-structures/tools for the fourth
result-view member and the ReadFileLine vocabulary, and expand the
Agent Note Testing section with the new rejection paths and the snapshot
evidence this PR carries.