fix(lower): route remaining bare-name sites through resolver + close 0102 [0102d]

Final 0102 sub-step. fix-0102c landed resolveBareCallee and routed the
primary call path + parameter target typing through it, leaving four other
bare-name consumer sites on the old first-wins path. Route the SAME resolver
through all four, gated exactly as the call path (plain top-level identifier,
no scope-mangle / UFCS alias / local shadow; act on .func / .ambiguous, fall
through on .none so single-author / local / std / qualified / foreign-single
resolution is byte-for-byte unchanged):

1. Default-argument expansion (expandCallDefaults): omitted trailing args
   fill from the RESOLVED author's defaults, not the winner's.
2. Function-value conversion (closure(fn) and the bare-fn-as-value func_ref /
   fn-ptr / closure-coercion path): captures the resolved author's FuncId.
3. Free-function UFCS (recv.fn() -> fn(recv, ...)): dispatches the resolved
   author for the receiver's source.
4. Comptime #run of a bare call: lowerMainAndComptime now sets
   current_source_file per decl, so a `NAME :: #run f()` in an imported
   module resolves f from THAT module's flat imports (own-author wins) instead
   of the main file's perspective (which made it spuriously ambiguous).

Regression tests: examples/0730-0734 (default-arg, closure+fn-value, UFCS,
comptime #run, UFCS-ambiguity), each fails on pre-fix code and passes after.
issues/0102-flat-import-same-signature-collision.md written RESOLVED with the
4-sub-step root cause and regression-test paths.

examples/expected/0730-modules-flat-same-name-default-arg.exit

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+0