fix: preserve literal prompt groups in memory data

[Grivn]

Summary

• escape every runtime-memory interpolation opener through a non-recursive prompt variable so arbitrary {{...}} text remains literal
• keep dynamic memory, evidence, document, and Provider run data out of subagent system personas
• cover empty, non-ASCII, whitespace, legal/unknown names, adjacent/nested, collision, and incomplete delimiter shapes

Verification

• pnpm run verify
• 343 tests passed; the Windows-only smoke test was skipped locally
• deterministic build, Headless activation, package contents, publint, and package type checks passed

Fixes #37