feat(ILO-399): modules — conditional imports via use ?<pred>

[danieljohnmorris]

Summary

• Adds compile-time conditional module selection with use ?<pred> "true-path" : "false-path"
• Three predicates: wasm (wasm32 target), native (host binary, default), test (ilo test runs)
• Resolver evaluates predicate against BuildTarget before any file I/O — only the selected branch is read

Syntax

use ?wasm "platform/wasm-io.ilo" : "platform/native-io.ilo"
use ?test "stubs/db-stub.ilo"    : "db/real-db.ilo"
use ?native "fast-native.ilo"    : "fallback.ilo"

Changes

• ast: UsePredicate enum (Wasm | Native | Test) + predicate: Option<UsePredicate> and alt_path: Option<String> fields on Decl::Use
• parser: detects ? after use, parses predicate ident, true path, :, false path; emits ILO-P016 for unknown predicates or malformed syntax
• resolver (main.rs): new BuildTarget enum with eval() method; resolve_imports takes build_target param and selects the branch before resolving
• examples/conditional-imports-wasm.ilo: usage documentation

Tests

• 8 new parser tests: parse_use_conditional_{wasm,native,test}, unknown predicate error, missing false branch, missing colon
• 4 new resolver tests: wasm true/false branch selection, test predicate, build_target_eval_all_predicates

Closes ILO-399. Extends ILO-60 (#627) and ILO-398.

Test plan

• cargo test — all tests pass (65 integration + 222 + 100 + 247 + 210 + 165 + 199 unit tests)
• Parser rejects unknown predicates with ILO-P016
• Resolver picks correct branch per BuildTarget

🤖 Generated with Claude Code

[danieljohnmorris]

needs manual rebase (conflicts in: src/main.rs)

[danieljohnmorris]

needs manual — rebase conflict in non-doc file(s)

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
687	1	686	0

View the full list of 1 ❄️ flaky test(s)

ilo::interpreter::tests::interpret_braced_guard_in_loop_no_early_return

Flake rate in main: 66.67% (Passed 1 times, Failed 2 times)

Stack Traces | 0.008s run time

thread 'interpreter::tests::interpret_braced_guard_in_loop_no_early_return' (32814) panicked at src/interpreter/mod.rs:10202:9:
parse errors: [ParseError { code: "ILO-P003", position: 27, span: Span { start: 35, end: 36 }, message: "expected `{`, got `;`", hint: Some("ilo bodies are single-line, `;`-separated — not python/swift-style indented. Use either the brace-block form `name p:t>r;{body1;body2}` or the single-line form `name p:t>r;body1;body2`. For statements that require a block (`@k xs{...}`, `wh cond{...}`, `?subj{...}`), the `{...}` must be on the same line as the head.") }]
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

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