ECMA-426 DecodeSourceMapSources reads a content slot only while its index
is within sourcesContent, so a shorter array leaves trailing sources
without content and a longer array adds no sources. Local application
analysis and browser collection rejected any length mismatch and dropped
every original from the map.
The content helper now checks only entry types. Browser collection drops
its separate check because the leaf schema already validates every
supplied entry, and the raw records are still budgeted before parsing.
Fixes#2821
Accept absent map-level sourcesContent and preserve null source-name slots alongside known originals and aligned content. Represent unnamed local declarations explicitly, retain leaf-local and flattened indices, and preserve declared indexed-section order across consumers.
Account for added indices before browser output allocation. Accept legacy retained rows without indices. Consolidate public CLI/MCP source-map fixtures and update the stale named-source-only assertion.
BREAKING CHANGE: Browser source-map original and mapping rows expose null for unavailable source names instead of inventing an unknown-source string. New index fields are optional when reading older retained evidence.
Refs #2023, #2024
Riley Gramlich