fix: SPDX headers and template placeholders (#22)

## Summary
- AGPL-3.0-or-later → PMPL-1.0-or-later in SPDX-License-Identifier lines
- Template placeholders replaced with actual values

Part of global TODO cleanup (2026-03-16).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath