bug: assembler does not rewrite relative dependency paths when copying libs to .labelle/deps/ #129

Summary

When the assembler copies local libs (e.g. from libs/needs_machine/) into .labelle/deps/labelle-needs_machine/, it preserves build.zig.zon files as-is without rewriting relative dependency paths. This causes transitive dependencies to resolve to the wrong location.

Repro

In flying-platform-labelle, both libs/needs_machine and libs/job_machine depend on labelle-fsm via a relative path:

// libs/needs_machine/build.zig.zon
.@"labelle-fsm" = .{
    .path = "../../../labelle-fsm",
},

From the original location (libs/needs_machine/), ../../../labelle-fsm correctly resolves up to labelle-toolkit/labelle-fsm.

After the assembler copies it to .labelle/deps/labelle-needs_machine/, the same ../../../labelle-fsm now resolves to flying-platform-labelle/labelle-fsm — which doesn't exist.

# Original (correct):
libs/needs_machine/ → ../../../labelle-fsm = labelle-toolkit/labelle-fsm ✓

# After copy (broken):
.labelle/deps/labelle-needs_machine/ → ../../../labelle-fsm = flying-platform-labelle/labelle-fsm ✗

Expected behavior

The assembler should rewrite relative .path dependencies in build.zig.zon when copying libs into .labelle/deps/, so they resolve correctly from the new location. Alternatively, transitive deps like labelle-fsm should also be copied into .labelle/deps/ and paths adjusted to point there.

Workaround

Symlink the dependency into the project root:

ln -s /path/to/labelle-toolkit/labelle-fsm /path/to/flying-platform-labelle/labelle-fsm