Share section classification across declaration analysis and mapping parsing. Preserve external URLs, malformed section reasons, section paths and safe sibling declarations without fetching nested maps.
Refs #5466. All 50 focused tests passed, including real CLI and stdio MCP regressions; typecheck and lint passed.
Share the ECMA-426 JSON parse view across fetched maps and local point tracing while retaining exact response text, bytes, and digest. Handle BOM and HTTP newline variants without treating unterminated prefixes as valid JSON.
Validation: 89 source-map tests passed; source/runtime build and check:fast passed. Real Chrome 154 CLI and stdio MCP browser verification passed on macOS ARM64.