Add ILTP canonical transaction packet architecture spec

[chrbailey]

Motivation

• Provide a concrete canonical deal-state object (ILTP) to replace Word/DocuSign/PMS as the source of truth and prevent downstream drift.
• Standardize a human-readable lease_packet.md (Markdown wrapper) with an embedded canonical YAML block so validators, generators, and agents can operate deterministically.

Description

• Add ILTP_SPEC.md documenting the ILTP design, including the recommended Markdown+YAML packet shape, field/evidence model, and artifact manifest strategy.
• Define an explicit state_machine and terminal states, validation tiers (blockers/consistency/risk), invariants (e.g., no DocuSign send while blockers exist, no PMS payload before signed lease), and artifact staleness rules.
• Specify mapping/profile-driven PMS integration (yardi_voyager_commercial_v1, appfolio_commercial_v1), DocuSign mapping concepts, the agent roles/operating model (Software 1.0/2.0/3.0), and an MVP rollout (validator, doc generation, DocuSign payload, PMS export).
• Provide a recommended repository layout and MVP implementation passes to guide follow-up implementation work.

Testing

• No automated unit or integration tests were executed as part of this PR; the change is an authored spec file only.
• The new file ILTP_SPEC.md was created and committed successfully (git commit completed without error).

---

Codex Task

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 66279d925f

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

Nest canonical sections under packet

The YAML example dedents at source, making all business sections siblings of packet instead of part of the canonical packet object. That structure is ambiguous for implementers and can lead validators/generators to hash or validate only packet metadata while silently ignoring source, parties, and other core fields, causing drift between tools built from this spec.

Useful? React with 👍 / 👎.