engine: a library-wrapped function kept in a const is registered where the const is handed over

[swapnilpaliwal-sd]

• export const plugin = wrap(async (app) => …) then host.register(plugin): the registration did not reach the literal, and path said the two were independent, although the literal handed over bare was reached.
• TypeScript (value-flow.dl): a const whose initializer is a boundary call handed a function passes that function on to a boundary call the const is handed to, by name or through an import. Excluded: a reassignment, a call through a project value, and a call whose typed result has no call signature.
• JavaScript (callbacks.dl): the same for a call rooted at a package import, carried as a libwrap value that is never a callee, so call classification is unchanged.
• Python has no hand-over edge even for a bare function, so it is not changed here.
• Tests: extended TS case 78 / hof-callback-at-library-boundary and JS case 34, each with a control (a const built from a plain value registers nothing). The TS case said "independent" before the fix.
• Checked: TS suite 97/97, JS suite 88/88, CLI cases (JS 236/236; TS 170/175, and those 5 fail identically on the base). Product: probes 29 → 31 of 73 with no regressions, edges 9988 → 10000 with none removed, index 43s vs 45s.