Finalize v1 platform stack spec pass

[snissn]

Summary

• Adds a near-top V1 Architecture Decisions section that selects platform EOA/KMS payer, FOC session keys, hosted coordinator, onchain registry/usage/receipt state, and Phase 0 gating for future modes.
• Adds a V1 Contract/API Surface with exact structs, functions, events, state transitions, access rules, and timeout/failure behavior.
• Adds a Phase 0 Compatibility Report Template with required tx hashes, pass/fail answers, SDK/tooling gaps, and the final recommended v1 mode.
• Updates README direction to match the selected v1 path.

Closes #1

Tests / checks

• rg -n "V1 Architecture Decisions|Section 6.7|V1 Contract/API Surface|Phase 0 Compatibility Report Template|Required Transaction Evidence|SDK and Tooling Gaps|Selected v1 target" spec.md README.md
• rg -n "Open options|exact storage layout remains open|option-preserving|must support multiple|Token Host generates registry|first supported FOC payer|first product default" spec.md README.md
• git diff --check

Benchmarks

Not applicable: documentation/spec-only change.

Notes

No contracts, coordinator code, SDK changes, or Token Host generation work are implemented in this PR. Smart-account payer, contract treasury payer, user-pays mode, direct browser upload, BYO coordinator, and proof/challenge finalization remain compatibility-gated future modes.

[Copilot]

Pull request overview

This PR updates the repository’s documentation to move spec.md from “option-preserving planning” to a more build-ready v1 direction by adding a near-top V1 decisions section, a normative v1 contract/API surface, and a Phase 0 compatibility report template; it also aligns the README’s “initial development direction” with that selected v1 path.

Changes:

• Adds a normative V1 Architecture Decisions section and reclassifies non-v1 modes as compatibility-gated or deferred.
• Introduces a detailed V1 Contract/API Surface (structs, events, errors, functions, access rules, transitions, timeout/failure behavior) plus a small platform API mapping.
• Adds a Phase 0 Compatibility Report Template and updates README direction to match the v1 target.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 11 comments.

File	Description
spec.md	Adds explicit v1 architecture decisions; defines a normative v1 contract/API surface and Phase 0 compatibility report template; rephrases previously open-ended sections to v1 + gated modes.
README.md	Updates the “Initial development direction” section to reflect the selected v1 mode and Phase 0 next step.

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[snissn]

@copilot review

[snissn]

Review-resolution update for latest head 65dcdf4:\n\n- Resolved all 11 Copilot review threads with replies.\n- Standardized v1 ABI naming on datasetId.\n- Added allowFailureCharges to PolicyConfig and tied failure charging behavior to it.\n- Added relayer management surface: setRelayer, isRelayer, and RelayerUpdated.\n- Added the nonzero receiptHash invariant for finalizeUpload.\n- Removed README/spec contradictions around the selected v1 path and clarified the older exploratory enum.\n\nChecks:\n- git diff --check origin/main...HEAD\n- rg -n "dataSetId|does not yet prescribe|authorized platform relayer|authorized relayer|option-preserving|must support multiple|exact storage layout remains open" spec.md README.md returned no matches.\n- Fresh Copilot cloud-agent run 26791714484 completed successfully on 65dcdf4.