fix(place): disable pin inflation and lower default padding

[zhaoxueyan1]

Problem

The ECC DreamPlace defaults still enabled pin-density inflation with pin_density=0.6 and requested cell_padding_x=300. That combination adds geometry inflation before placement even when the user has not explicitly enabled pin inflation.

Change

• Set pin_density to -1, which keeps pin-density inflation disabled unless a workspace explicitly supplies a value in (0, 1).
• Reduce the default cell_padding_x from 300 to 200 for the ICS55/general DreamPlace defaults.
• Keep the parameter schema, generated DreamPlace JSON, tests, and English/Chinese configuration documentation consistent.

The existing SG13G2-specific template default of cell_padding_x=0 is unchanged.

Validation

• pytest -q test/data/test_design_parameters.py test/formal/test_param_propagation.py test/cli/params/test_registry.py
  • 416 passed, 3 skipped, 1 xfailed
• Parsed dreamplace_ecc.json successfully and verified the effective defaults are cell_padding_x=200 and pin_density=-1.
• git diff --check

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