feat(p3): cross-component stream<T> pairing detection (#141, ADR-3)

CHANGELOG.md

@@ -4,6 +4,32 @@ All notable changes to this project will be documented in this file.
 
 ## [Unreleased]
 
+### Added
+
+- **Cross-component `stream<T>` pairing detection** (issue #141,
+  ADR-3, `meld-core/src/p3_stream.rs`). Foundation for the in-module
+  stream adapter: when meld fuses two components that share a
+  `stream<T>` endpoint, today both sides still route every chunk
+  through host `pulseengine:async` imports. This PR adds the
+  detection half — a `StreamPairGraph` built at resolve time that
+  inventories which fused components form producer → consumer stream
+  pairings. The graph is attached to `DependencyGraph` next to the
+  resource graph. A `StreamPair` is a conservative *candidate*: it is
+  recorded only when two fusion-connected components have
+  complementary roles (one `StreamWrite`, one `StreamRead`) on a
+  stream of the **same element type** — pairing on matching element
+  type is the line between an honest candidate and a hallucinated
+  one. The ring-buffer (same-memory) and copy-chain (cross-memory)
+  adapter *emitter* is a runtime-verified follow-up (ADR-3 Path N);
+  cross-component stream codegen is only correct once executed on a
+  real runtime, so it is deliberately not in this PR. ADR-3 records
+  the design; SR-33's detection half is satisfied here, the codegen
+  half by the follow-up. 9 unit tests including the 4 ADR-3 gating
+  fixtures. Registering `p3_stream.rs` in the Mythos Tier-5 path
+  lists is a separate follow-up — claude-code-action self-validates
+  that the invoking workflow matches `main`, so a PR cannot both
+  modify `mythos-auto.yml` and be scanned by it.
+
 ### Changed
 
 - **CI workflows now skip on docs/safety-only changes**

meld-core/src/lib.rs

@@ -47,6 +47,7 @@ pub mod component_wrap;
 mod error;
 pub mod merger;
 pub mod p3_async;
+pub mod p3_stream;
 pub mod parser;
 pub mod resolver;
 pub mod resource_graph;

meld-core/src/merger.rs

@@ -3692,6 +3692,7 @@ mod tests {
             adapter_sites: Vec::new(),
             module_resolutions: Vec::new(),
             resource_graph: None,
+            stream_pair_graph: None,
             reexporter_components: Vec::new(),
             reexporter_resources: Vec::new(),
             unresolved_imports: vec![
@@ -3906,6 +3907,7 @@ mod tests {
             adapter_sites: Vec::new(),
             module_resolutions: Vec::new(),
             resource_graph: None,
+            stream_pair_graph: None,
             reexporter_components: Vec::new(),
             reexporter_resources: Vec::new(),
             unresolved_imports: vec![
@@ -3958,6 +3960,7 @@ mod tests {
             adapter_sites: Vec::new(),
             module_resolutions: Vec::new(),
             resource_graph: None,
+            stream_pair_graph: None,
             reexporter_components: Vec::new(),
             reexporter_resources: Vec::new(),
             unresolved_imports: vec![
@@ -4018,6 +4021,7 @@ mod tests {
             adapter_sites: Vec::new(),
             module_resolutions: Vec::new(),
             resource_graph: None,
+            stream_pair_graph: None,
             reexporter_components: Vec::new(),
             reexporter_resources: Vec::new(),
             unresolved_imports: vec![
@@ -4069,6 +4073,7 @@ mod tests {
             adapter_sites: Vec::new(),
             module_resolutions: Vec::new(),
             resource_graph: None,
+            stream_pair_graph: None,
             reexporter_components: Vec::new(),
             reexporter_resources: Vec::new(),
             unresolved_imports: vec![
@@ -4124,6 +4129,7 @@ mod tests {
             adapter_sites: Vec::new(),
             module_resolutions: Vec::new(),
             resource_graph: None,
+            stream_pair_graph: None,
             reexporter_components: Vec::new(),
             reexporter_resources: Vec::new(),
             unresolved_imports: vec![
@@ -4256,6 +4262,7 @@ mod tests {
             adapter_sites: Vec::new(),
             module_resolutions: Vec::new(),
             resource_graph: None,
+            stream_pair_graph: None,
             reexporter_components: Vec::new(),
             reexporter_resources: Vec::new(),
             unresolved_imports: vec![
@@ -4414,6 +4421,7 @@ mod tests {
             adapter_sites: Vec::new(),
             module_resolutions: Vec::new(),
             resource_graph: None,
+            stream_pair_graph: None,
             reexporter_components: Vec::new(),
             reexporter_resources: Vec::new(),
             unresolved_imports: vec![
@@ -4565,6 +4573,7 @@ mod tests {
             adapter_sites: Vec::new(),
             module_resolutions: Vec::new(),
             resource_graph: None,
+            stream_pair_graph: None,
             reexporter_components: Vec::new(),
             reexporter_resources: Vec::new(),
             unresolved_imports: vec![