Add Echo Target IR lowering

[flyingrobots]

Summary

• add the first edict_syntax Target IR lowering surface for echo.dpo@1 -> echo.span-ir/v1
• emit deterministic in-memory Echo Span IR review artifacts for the supported effectful Core shape
• reject non-Echo targets and unsupported Core nodes with stable TargetLoweringFailureKind values before producing artifacts
• derive Target IR lowering facts from native TargetProfileFacts so lowerability evidence feeds the same Echo intrinsic selection
• add the docs/topics/target-ir/ topic shelf and update roadmap/changelog signposts; git-warp is recorded as the next target after Echo

RED/GREEN

• RED: cargo test -p edict-syntax --test target_ir failed on unresolved Target IR API
• GREEN: cargo test -p edict-syntax --test target_ir
• RED: cargo test -p edict-syntax --test target_ir lowerability_native_support_feeds_echo_target_lowering failed on missing TargetIrLoweringFacts::from_target_profile_facts
• GREEN: cargo test -p edict-syntax --test target_ir lowerability_native_support_feeds_echo_target_lowering

Verification

• cargo test -p edict-syntax --test target_ir
• cargo xtask contract-check
• markdownlint-cli2 CHANGELOG.md ROADMAP.md docs/topics/README.md docs/topics/target-ir/README.md docs/topics/target-ir/test-plan.md
• cargo xtask verify

Boundaries

• no Echo runtime execution
• no admission workflow
• no general target-lowering plugin dispatch
• no git-warp lowering in this PR; gitwarp.ref_crdt@1 is next after Echo
• no v2 chained or composite adapter resolution

Closes #66

[flyingrobots]

@codex review

[coderabbitai]

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: fb478b08-6055-49cb-b264-ed06aff8c4cb

📥 Commits

Reviewing files that changed from the base of the PR and between d6f9225 and b2671fe.

📒 Files selected for processing (9)

• CHANGELOG.md
• crates/edict-syntax/src/lowerability.rs
• crates/edict-syntax/src/target_ir.rs
• crates/edict-syntax/tests/lowerability.rs
• crates/edict-syntax/tests/target_ir.rs
• docs/topics/lowerability/README.md
• docs/topics/lowerability/test-plan.md
• docs/topics/target-ir/README.md
• docs/topics/target-ir/test-plan.md

Walkthrough

Introduces the first Target IR lowering surface in edict-syntax: a new target_ir module that emits deterministic echo.span-ir/v1 artifacts from supported Core shapes for echo.dpo@1. LowerabilityReport gains an operation_profile field. A 538-line test suite and full documentation/test-plan accompany the implementation.

Changes

Echo Target IR Lowering Pipeline

Layer / File(s)	Summary
LowerabilityReport operation_profile extension crates/edict-syntax/src/lowerability.rs, crates/edict-syntax/tests/lowerability.rs, docs/topics/lowerability/README.md, docs/topics/lowerability/test-plan.md	Adds operation_profile: String to LowerabilityReport, populates it in check_lowerability, adds a test assertion for the expected value, and expands the public-surface docs to reflect the new field.
Target IR data structures and artifact model crates/edict-syntax/src/target_ir.rs (lines 1–145)	Defines ECHO_DPO_TARGET_PROFILE/ECHO_SPAN_IR_DOMAIN constants and all public data types: TargetIrLoweringFacts, TargetEffectLowering, TargetLoweringStatus, TargetLoweringFailureKind (12 variants), TargetLoweringFailure, TargetLoweringReport, TargetIrArtifact, TargetIrIntent, TargetIrStep.
lower_to_target_ir validation and lowering pipeline crates/edict-syntax/src/target_ir.rs (lines 146–403)	Implements target-selection validation, Core ABI/capability checks, per-intent lowering (lower_intent), CoreNode dispatch (rejecting Let, mapping Effect to steps), effect-to-intrinsic resolution with structured diagnostics, and unsupported-report construction helpers.
Crate root wiring crates/edict-syntax/src/lib.rs	Declares pub mod target_ir and re-exports all new types and constants; updates crate-level docs to mention Echo Target IR lowering and enumerate deferred responsibilities.
Target IR test suite crates/edict-syntax/tests/target_ir.rs	538-line suite with fixture sources, Core/context/facts builders, 12 named tests covering successful lowering, native-lowerability bridging, semantic preservation (obstruction arms, intent results, chained bindings), and negative cases for every TargetLoweringFailureKind.
Docs, test plan, changelog, and roadmap docs/topics/target-ir/*, docs/topics/README.md, CHANGELOG.md, ROADMAP.md	Adds Target IR topic chapter and test plan; inserts entry in the topics index; updates changelog with stable failure semantics; expands v0.9.0-alpha.1 roadmap milestone with concrete identifiers, scope bullets, and a git-warp non-goal.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~60 minutes

Possibly related PRs

• flyingrobots/edict#37: Introduced the typed lowerability.rs / check_lowerability / LowerabilityReport model that this PR directly extends with operation_profile and feeds into TargetIrLoweringFacts::from_lowerability_report.

Poem

⚡ echo.dpo@1 heard the call,
Spanned its IR down the hall.
CoreNode::Let? Rejected. Cold.
Twelve failure kinds, precisely told.
No runtime ran, no git-warp crept—
Just deterministic steps, perfectly kept. 🎯

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 79.07% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise and accurately names the main change: Echo Target IR lowering.
Description check	✅ Passed	The description is directly related to the PR and summarizes the Target IR lowering work.
Linked Issues check	✅ Passed	The implemented Target IR pipeline, docs, tests, and lowerability bridge align with #66's scope and exit criteria.
Out of Scope Changes check	✅ Passed	No clear out-of-scope code changes are present; the docs, tests, and API updates all support the Echo Target IR slice.

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[flyingrobots]

@codex review please

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 1f3923da83

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".

[flyingrobots]

@codex second opinion requested on this self-discovered issue before I fix it.

ID	Severity	Source	File	Lines	Issue	Planned mitigation
SELF-001	P3	Self-audit/local gate	crates/edict-syntax/src/target_ir.rs	lower_to_target_ir	cargo xtask verify fails Clippy too_many_lines after the review-feedback fixes expanded the function to 103 lines.	Extract small helpers for target/profile validation or intent lowering without changing public behavior, then rerun focused target-IR tests and cargo xtask verify.

[flyingrobots]

Activity Summary

ID	Severity	Source	File	Commit	Outcome
1	P2	PR	crates/edict-syntax/src/target_ir.rs	8177d39	Target IR facts now derive from selected native lowerability results instead of carrying unselected native effect support.
2	P2	PR	crates/edict-syntax/src/target_ir.rs	e43fd11	Echo Target IR steps preserve structured obstruction arms, not just failure keys.
3	P2	PR	crates/edict-syntax/src/target_ir.rs	fc3e93e	Target IR intents preserve result expressions.
4	P2	PR	crates/edict-syntax/src/target_ir.rs	dcc1f75	Target IR steps preserve effect result bindings for data dependencies.
5	P2	PR	crates/edict-syntax/src/target_ir.rs	8cd979f	Target lowering validates operation-profile support before emitting artifacts.
6	P2	PR	crates/edict-syntax/src/target_ir.rs	c3f47b0	Empty target-step intents reject with NoTargetSteps instead of producing empty artifacts.
SELF-001	P3	Self	crates/edict-syntax/src/target_ir.rs	bdd3fb8	Split target-lowering helpers so cargo xtask verify passes Clippy without lint exceptions.

Verification after fixes:

• cargo test -p edict-syntax --test target_ir
• cargo xtask contract-check
• markdownlint-cli2 CHANGELOG.md ROADMAP.md docs/topics/README.md docs/topics/target-ir/README.md docs/topics/target-ir/test-plan.md
• cargo xtask verify

[flyingrobots]

@codex review please