docs: seed docs/proof-debt.md index per trusted-base policy (#74)

## Summary
- Adds a thin, schema-conformant index at `docs/proof-debt.md`.
- References [`PROOF-NEEDS.md`](./PROOF-NEEDS.md) as the source of truth
— no content duplication.
- P1 seed in the [trusted-base reduction
policy](hyperpolymath/standards#203) chain.

## What this PR does NOT do
Migrate the substantive content out of `PROOF-NEEDS.md`. That file
remains canonical; this file just makes the schema-conformant filename
exist for the
[`check-trusted-base.sh`](hyperpolymath/standards#211)
CI gate.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

docs/proof-debt.md

@@ -0,0 +1,59 @@
+<!--
+SPDX-License-Identifier: MPL-2.0
+SPDX-FileCopyrightText: 2026 Jonathan D.A. Jewell (hyperpolymath)
+-->
+
+# Proof Debt — proven
+
+**Schema**: [hyperpolymath/standards `TRUSTED-BASE-REDUCTION-POLICY.adoc`](https://github.com/hyperpolymath/standards/blob/main/docs/TRUSTED-BASE-REDUCTION-POLICY.adoc) (standards#203).
+
+This file is the schema-conformant **index** for this repo's proof
+debt. The substantive content lives in
+[`PROOF-NEEDS.md`](../PROOF-NEEDS.md) — keep that file as the source of truth
+and use this one as the schema bridge for the
+`check-trusted-base.sh` CI gate ([standards#211](https://github.com/hyperpolymath/standards/pull/211)).
+
+## Marker count (2026-05-26)
+
+10 soundness-relevant escape hatches detected by
+`scripts/check-trusted-base.sh`. See `PROOF-NEEDS.md` for the per-site
+classification rationale.
+
+## (a) DISCHARGED in this repo
+
+See `PROOF-NEEDS.md` — any markers no longer present in source.
+
+## (b) BUDGETED — tested with a refutation budget
+
+See `PROOF-NEEDS.md` — markers at FFI / extraction boundaries with
+documented property-test budgets.
+
+## (c) NECESSARY AXIOM
+
+See `PROOF-NEEDS.md` — markers that encode metatheoretic assumptions.
+
+## (d) DEBT — actively to be closed
+
+See `PROOF-NEEDS.md` — markers still owed a proof or a §(b)/§(c)
+classification.
+
+## How to update this file
+
+When markers change in source:
+
+1. Update `PROOF-NEEDS.md` first (source of truth).
+2. If the marker count changes substantially, update the count above
+   so this index doesn't drift.
+3. The `check-trusted-base` CI gate (standards#211) reads BOTH
+   `docs/proof-debt.md` AND `PROOF-NEEDS.md` for documentation lookups,
+   so the index can stay light.
+
+## Companion documents
+
+- [standards#195](https://github.com/hyperpolymath/standards/pull/195) — estate proof-debt audit.
+- [standards#203](https://github.com/hyperpolymath/standards/pull/203) — trusted-base reduction policy (the schema).
+- [`PROOF-NEEDS.md`](../PROOF-NEEDS.md) — this repo's substantive proof-debt audit (source of truth).
+
+---
+
+🤖 Schema-conformant index seeded by Claude Code, 2026-05-26.