pyvm: split op handlers into ops_core/ops_box/ops_ctrl; add ops_flow + intrinsic; delegate vm.py without behavior change

net-plugin: modularize constants (consts.rs) and sockets (sockets.rs); remove legacy commented socket code; fix unused imports
mir: move instruction unit tests to tests/mir_instruction_unit.rs (file lean-up); no semantic changes
runner/pyvm: ensure using pre-strip; misc docs updates

Build: cargo build ok; legacy cfg warnings remain as before

docs/design/flow-blocks.md

@@ -0,0 +1,81 @@
+# Flow Blocks and Arrow Piping (Design Draft)
+
+Status: design-only during freeze (no implementation)
+
+Goal
+- Make control/data flow visually obvious while keeping the core minimal.
+- Core = anonymous `{ ... }` blocks + `->` chaining with `_` or `|args|` as the input placeholder.
+- Always desugar to plain sequential let/if/call; zero new runtime constructs.
+
+Core Syntax
+- Serial (value flow):
+  ```nyash
+  { readConfig() }
+    -> { |cfg| validate(cfg) }
+    -> { |cfg| normalize(cfg) }
+    -> { |cfg| save(cfg) }
+  ```
+- Placeholder short form:
+  ```nyash
+  { fetch() } -> { process(_) } -> { output(_) }
+  ```
+- If/Else with horizontal flow:
+  ```nyash
+  if cond -> { doA() } else -> { doB() }
+  ```
+
+Semantics
+- `{ ... }` is an anonymous scope usable as expression or statement.
+- `->` passes the left result as the first parameter of the right block.
+- Left returns `Void` → right cannot use `_`/`|x|` (compile-time error in MVP spec).
+- `_` and `|x,...|` are exclusive; mixing is an error.
+
+Lowering (always zero-cost sugar)
+- Chain desugars to temporaries and calls:
+  ```nyash
+  # {A} -> { |x| B(x) } -> { |y| C(y) }
+  t0 = A();
+  t1 = B(t0);
+  t2 = C(t1);
+  ```
+- If/Else chain desugars to standard if/else blocks; merges follow normal PHI wiring rules.
+
+Match normalization via guard chains
+- Prefer a single readable form:
+  ```nyash
+  guard cond1 -> { A }
+  guard cond2 -> { B }
+  else        -> { C }
+  ```
+- Lowers to first-match if/else chain. No new pattern engine is introduced.
+
+Range and CharClass guards (design)
+- Range: `guard ch in '0'..'9' -> { ... }` → `('0' <= ch && ch <= '9')`.
+- CharClass: `guard ch in Digit -> { ... }` → expands to ranges (e.g., '0'..'9').
+- Multiple ranges combine with OR.
+
+Formatting (nyfmt guidance)
+- Align arrows vertically; one step per line:
+  ```
+  { fetch() }
+    -> { validate(_) }
+    -> { save(_) }
+  ```
+- Suggest factoring when chains exceed N steps; prefer naming a scope helper.
+
+Observability (design only)
+- `NYASH_FLOW_TRACE=1` prints the desugared steps (`t0=...; t1=...;`).
+
+Constraints (MVP)
+- No new closures; anonymous blocks inline when capture-free.
+- Recursion not required; focus on linear/branching chains.
+- ASI: treat `->` as a low-precedence line-continue operator.
+
+Tests (syntax-only smokes; design)
+- flow_linear: `read→validate→save` matches expected value.
+- flow_placeholder: `{f()} -> { process(_) } -> { out(_) }`.
+- flow_if: `if cond -> {A} else -> {B}` behaves like standard if.
+
+Freeze note
+- Documentation and design intent only. Implementation is deferred until after the freeze.
+