Migrated from Method backlog

This issue was created from a legacy filesystem backlog card. GitHub Issues are now the live work tracker; repository docs remain Method evidence.

Source backlog: docs/method/backlog/asap/PLATFORM_contract-hosted-file-history-substrate.md
Original lane: asap
Original legend: PLATFORM

Original backlog card

Contract-Hosted File History Substrate

Status: active sequencing card.

Design packet:
0018 - Contract-Hosted File History Substrate

Source request:
request.md

Why now

PR #326 established the first Echo/Wesley contract-hosting roadmap. The next
body of work makes that path real enough for a jedit-like contract without
turning Echo into a text editor substrate.

The core doctrine remains strict: Echo hosts generated application contracts
through generic deterministic surfaces. jedit supplies the proof fixture and
consumer shape.

Sequence

1. Installed Wesley contract host dispatch
   • Status: local package dispatch proof complete.
2. Contract QueryView observer bridge
   • Status: core bridge, generated helpers, package registry boundary, and
     local dispatch proof complete.
3. Contract-aware receipts and readings
4. Contract reading identity and bounded payloads
5. Contract artifact retention in echo-cas
6. Contract retention and semantic lookup seams
7. External contract proof fixture
8. Intent-only contract runtime mutations
9. Generic contract braid substrate
10. Contract inverse admission hook

Acceptance criteria

• The source request is archived in docs.
• The design packet captures doctrine, non-goals, missing substrate, and
  execution order.
• Each implementation slice has a narrow backlog card with RED/GREEN acceptance
  criteria.
• The sequence preserves the rule that application nouns stay out of Echo core.

Non-goals

• Do not implement runtime code in this sequencing card.
• Do not add text, rope, editor, Graft, or jedit APIs to Echo core.
• Do not replace the existing Echo contract-hosting roadmap; extend it.