Result: done
Files: crates/nikaia-std/src/tools/grammar_run.nika crates/nikaia-std/src/tools/lowered/grammar_run.rs crates/nikaia-std/src/tools/lowered.rs crates/nikaia/src/grammar_run.rs scripts/self_hosting.py docs/selfhosting-plan.md
Commit: grammar run: the parser’s build and run move into Nikaia (GR)
Body: compile_and_run, cargo and write_if_changed move to tools/grammar_run.nika as grammar_run_compile_and_run and grammar_run_write_if_changed, over process::run, hash::sha256_hex, env::var and fs with fs::Root::Anywhere. The host trait GrammarRunHost has driver, manifest, shared_target and where_tools_start. A host method that throws lowers to Box<dyn Error>, so the Rust host keeps the driver’s own Wall in a RefCell and Workshop::run returns it after the call; the Nikaia side rethrows NowhereToBuild there, and that value is never seen. Workshop::run keeps its Mutex guard and calls the lowered function through block_on, which works inside a comptime evaluation (the it grammar tests ran real builds). The file gets an impl Error for CheckWall (needed to throw it), which also gives Wall a Display. The unchanged-file check reuses sysroot_holds (sysroot_cache.nika), because String? == String is refused (NK1102). Messages stay byte for byte, but {error} is now an io::IoError’s text and not Rust’s io::Error’s. process::run throws on output that is not UTF-8, where Rust read it lossily. Stays Rust: Ask, Workshop and its Mutex/OnceLock, run_comptime, driver, dumper, shapes, decode, and shared_target and manifest as host methods (they move with O1).
Part: #125
Pushed: local b070adb974fbfab6ded44c4709efd92e43752b7d
Tests: it grammar_at_build_time dsl_grammar build_time comptime 115 passed; --lib grammar_run:: 0 tests; clippy, cargo fmt, pre-push-check green; lower-std fixpoint: only grammar_run.rs and its lowered.rs index lines are mine. Not run: tests/compiler as a whole (left to the driver’s suite). No existing test prints the texts running cargo: …, creating …, writing …, running <binary>: …, a failed cargo’s stderr or DidNotBuild (no failing cargo can be staged offline).
Gate: green
Deviation: none
Found: none
Needs: lower-std with the freshly built binary rewrites lowered/project_members.rs (TrustedMap -> HashMap) and lowered/check_core_ops.rs (another agent’s .nika is modified). Neither is mine; both left uncommitted.
Changelog: none
Owner: none
Disk freed: 0
Rs2nika: kept 9 of 51 lines; costliest edits: the Command::new(..).arg(..)...output() chains rewritten as process::run(program, [args]; dir:); .map_err(fn(error) {..}) turned into catch { throw CheckWall::.. } with display() in f-strings; the impl Workshop method over parsed/ask turned into a free function over host.driver()/host.manifest()/host.shared_target(). The draft also held the unmoved shared_target.
