minimal handling of inventory power tokens in Nim agents

[relh]

Observation tokens changed their format and now have p1 and p2 for base-256 encoded amounts

• Old format: only inv:<resource> existed, so values >255 were truncated. New format: multi-token inv:<resource>:p1, inv:<resource>:p2 are emitted when amounts exceed the base, extending the range.
• Describe inventory encoding: inv:<resource> stores amount % 256, inv:<resource>:p1 stores (amount / 256) % 256, and inv:<resource>:p2 stores (amount / 256^2) % 256.
• Why for Dinky: recent refactors emit the new power tokens; Nim agents were treating them as unknown features and reading only the base token, causing warnings and incorrect inventory values. This change maps and reconstructs the full amount.

Testing

• Not run (not requested)

[relh]

• minimal handling of inventory power tokens in Nim agents #4529 👈 (View in Graphite)
• main

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