Add poem on WeftMark, creative mathematics, and language as a machine

[tabenius]

Adds docs/poem.md, a poem, "The Weft and the Delta," about WeftMark and about programming as creative mathematics and language as a computing machine.

It weaves the requested imagery into WeftMark's own themes:

• The weft/warp loom — the warp as Git lineage (what is granted), the weft as the deliberate change, the mark as the recorded reason, evidence, and review readiness.
• Akka — actors as sealed, share-nothing message passers, and stream backpressure as the discipline that keeps a busy merge from becoming a storm.
• Water flowing — the river that follows the path of least resistance, a will composed of independent droplets.
• Delta meandering — braided channels depositing silt as a ledger, the river's recorded argument with the land, mapped as lineage.

Documentation-only change; no code or runtime behavior is affected.

🤖 Generated with Claude Code

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Generated by Claude Code