Give PoissonRecon a writable temporary directory

[Xananthium]

Problem

PoissonRecon stores its out-of-core PR_* scratch files in --tempDir, then $TMPDIR, then the process working directory. ODM already knows a writable mesh output directory, but did not pass it to PoissonRecon.

This makes an otherwise resumable mesh stage fail when ODM is launched by a service manager with a non-writable working directory (for example /). Reducing the Poisson thread count cannot repair that filesystem failure, so every retry fails before ReconstructMesh sees a dirty mesh.

Change

Pass the absolute output-mesh directory to PoissonRecon through its existing --tempDir option. This keeps scratch files beside the dirty mesh and leaves the public Python API and retry behavior unchanged.

A focused unit test captures the generated commands and covers a writable output path containing a space.

Verification

• New regression test passes.
• Full ODM unit suite: 22 passed in a native ODM 3.6.1 environment.
• The failure mode was source-traced to PoissonRecon's $TMPDIR / ./ fallback and mkstemp use, then independently recovered in a 24,136,575-point run by supplying a writable working directory.

No container-specific behavior or new dependency is introduced.