iter clippy-sweep: clear all 61 cargo clippy warnings

Hygiene sweep across the workspace under `cargo clippy --workspace
--all-targets`. Before: 61 warnings. After: zero. Tests stay 563
green, `cargo doc` stays at zero warnings, and all three bench
scripts exit 0 against existing baselines.

Twelve lint classes, three fix shapes:

- Documentation hygiene (~32 hits): `doc_lazy_continuation` resolved
  by adding blank lines before continuation paragraphs or rephrasing
  the offending line; plus four `empty_line_after_doc_comments` hits
  in workspace.rs where eight `///` blocks left orphan by form-a.1
  T5 test relocation were converted to plain `//`.
- Idiomatic refactors (~16 hits): `.err().expect()` → `.expect_err()`,
  redundant `.into_iter()` and `.into()` removed, `|f| g(f)` →
  `g`, `.trim().split_whitespace()` → `.split_whitespace()`,
  `push_str("x")` → `push('x')`, two manual `impl Default` flipped
  to `#[derive(Default)]` + `#[default]`, two nested `if let Some(_)
  = …` collapsed.
- Block extraction (1 hit): a 13-line block inside an `else if`
  condition in synth's Var-arm extracted to a new helper
  `is_class_method_dispatch(name, env)` next to
  `qualifier_is_class_shape`.

Three `#[allow]`s with inline rationale where clippy's suggestion
would lose meaning: `only_used_in_recursion` on walk_pattern (the
parameter preserves the five-fn walker-framework signature
uniformity), 2× `if_same_then_else` on qualify_local_types shapes
(two branches encode semantically distinct disqualification
reasons), `too_many_arguments` on `Emitter::new` (8 workspace-flat
tables; bundling would just rename boilerplate).

docs/journals/INDEX.md

@@ -60,3 +60,4 @@
 - 2026-05-13 — iter str-concat: `str_concat : (borrow Str, borrow Str) -> Str` heap-Str concatenation primitive shipped in four-site lockstep, closing fieldtest-form-a friction finding #4. T1 RED-pin `crates/ail/tests/str_concat_e2e.rs` + new corpus fixture `examples/show_user_adt_with_label.ail` (Show user-ADT body using `(app str_concat "Item " (app int_to_str n))` through prelude `print`; ok 23/2). T2 `runtime/str.c` C helper `ailang_str_concat(a, b)` appended after `ailang_str_clone`: reads `len` headers from both source payloads, `str_alloc(la+lb)`, memcpys both bytes, NUL-terminates. T3 `crates/ailang-check/src/builtins.rs` install entry (Type::Fn arity-2 Borrow-Borrow params, Own return, effects empty) + list() row + `install_str_concat_signature` unit test reaching into `env.globals` directly (deeper than synth_in_builtins_env-based siblings because first builtin with arity-2 Borrow params). T4 `crates/ailang-codegen/src/lib.rs` four-site lockstep: extern `declare ptr @ailang_str_concat(ptr, ptr)` after str_clone declare + lower_app arm after str_clone arm (arity-2 check + two `lower_term` + `fresh_ssa` + body push) + `is_builtin_callable` match-list extended with `"str_concat"` + IR-pin unit test `str_concat_emits_call_to_ailang_str_concat` asserting both extern declaration AND call instruction in emitted IR. Five IR snapshots regenerated (`hello.ll`, `list.ll`, `max3.ll`, `sum.ll`, `ws_main.ll`) to absorb the new unconditional declare line in IR header — same upkeep pattern as hs.4 (sole diff verified at IR line 17 across all snapshots). T5 lockstep-collision repair: `examples/bug_unbound_in_instance_method.ail` had used `str_concat` as the literal UNBOUND name (because that was the fieldtester's LLM-natural repro); renamed to `format_label` (LLM-author-realistic helper name that will never become a builtin) and updated `crates/ail/tests/unbound_in_instance_method_pin.rs` (`replace_all` on `str_concat` → `format_label`, including one test name flipped to `check_fires_unbound_var_for_format_label_in_instance_method_body`), preserving the regression guard's intent (instance-method-body walked through unbound-var check) while substituting a name with stable unbound semantics. T6 `docs/DESIGN.md` new §"Heap-Str primitives" subsection (line 1994) between the milestone-24 Show-backer enumeration and the existing `Primitive output goes through ...` paragraph, cataloguing all five heap-Str primitives (`int_to_str`, `bool_to_str`, `float_to_str`, `str_clone`, `str_concat`) with type signatures, iter origins, and the user-visible-vs-prelude-internal distinction; Show-backer block unchanged. T7 `docs/roadmap.md` struck `[x] [feature] str_concat` line at end of P2 cluster. Two minor plan-vs-actual discrepancies recorded in journal Concerns: (a) T3 Step 5 test-count prediction `passed: 560 failed: 1` was actual `passed: 558 failed: 3` because the unbound_in_instance_method_pin tests turn RED at checker registration not at codegen (assertion is on the `[unbound-var]` diagnostic which depends only on the checker registry) — implementation correct, T5 fully repairs; (b) IR snapshot regen for T4 was not explicitly scripted in the plan but follows hs.4 precedent. Final iter state: 562/562 green (559 baseline + 3 new pins), zero re-loops across all 7 tasks. Bench impact none (no new code paths touched by bench corpus; bench fixtures use `int_to_str` / `bool_to_str` only). Closes fieldtest-form-a queue: bug (closed bugfix-instance-body-unbound-var), spec_gaps 2+3 (closed form-a.tidy), friction (closed here). Remaining open: spec_gap 1 dropped per recon (audit-form-a "plan two sites" claim did not match HEAD) → 2026-05-13-iter-str-concat.md
 - 2026-05-13 — iter rustdoc-sweep: cleared all 23 `cargo doc --workspace --no-deps` warnings (17 in `ailang-check` + 4 in `ailang-core` + 2 in `ailang-surface`). Two warning classes: (a) `pub` doc-comments that linked-via-brackets to `pub(crate)`/private items (15 hits) — replaced ``[`fn`]`` with plain backtick-code-span ``` `fn` ``` so the identifier stays readable but rustdoc no longer tries to resolve the link; (b) unresolved/ambiguous links (8 hits) — `mono.rs` `[`Registry`]`/`[`Registry::entries`]` ×3 fully-qualified to `[`ailang_core::workspace::Registry…`]`; `loader.rs` `[`crate::parse`]` ×2 (ambiguous between fn + mod) disambiguated to `[`crate::parse()`]`; `lib.rs` `metas[i]` (parsed as a link) escaped to `metas\[i\]`. Tests 562 → 562, no behaviour change → 2026-05-13-iter-rustdoc-sweep.md
 - 2026-05-13 — iter drift-test-narrowing: `crates/ailang-core/tests/design_schema_drift.rs` now scans §"Data model" only, not the whole DESIGN.md. New helper `data_model_section()` slices `DESIGN_MD` from `## Data model` to the next top-level `## ` header; all 7 anchor-presence tests switched from `DESIGN_MD.contains(anchor)` to `data_model_section().contains(anchor)`. Closes the audit-form-a-precursor `[high]` "anchors-elsewhere-pass-silently" failure mode (an anchor present only in §"Decision 11" or another discussion section was previously treated as documented). All 38 anchors verified pre-edit to live in §"Data model" so the tightening doesn't regress to red. New pin `data_model_section_is_bounded` (starts-with `## Data model`, no bleed past `\n## Pipeline`, > 1 KB) guards the extractor itself against silent regression to whole-document scanning. Tests 562 → 563 (+1) → 2026-05-13-iter-drift-test-narrowing.md
+- 2026-05-14 — iter clippy-sweep: cleared all 61 `cargo clippy --workspace --all-targets` warnings across 12 lint classes. Bulk: 32× `doc_lazy_continuation` + 4× `empty_line_after_doc_comments` (8 orphan `///` blocks in `workspace.rs` left by form-a.1 T5 relocation converted to plain `//`) — pure documentation hygiene. Idiomatic refactors: 5× `err_expect` (`.err().expect()` → `.expect_err()`), 3× `useless_conversion`, 2× `redundant_closure`, 2× `collapsible_match`, 1× `single_char_add_str`, 1× `trim_split_whitespace`. Two `derivable_impls` (manual `Default` for `ParamMode` + `AllocStrategy` flipped to `#[derive(Default)]` + `#[default]`). One `blocks_in_conditions` extracted to a new helper `is_class_method_dispatch(name, env)` next to `qualifier_is_class_shape` in `check/src/lib.rs`. Three `#[allow]`s with inline rationale: `only_used_in_recursion` on `walk_pattern` (preserves the 5-fn walker-framework signature uniformity), 2× `if_same_then_else` on `qualify_local_types` shapes (`check/src/lib.rs:3457` + `codegen/src/subst.rs:165` — the two `name.clone()` branches encode semantically distinct disqualification reasons), `too_many_arguments` on `Emitter::new` (8 workspace-flat tables; bundling would just rename boilerplate). Tests 563 → 563 (no behavior change); `cargo doc` stays at 0 warnings (rustdoc-sweep baseline holds); all 3 bench scripts exit 0 against existing baselines (free stability check that the sweep touched no semantics) → 2026-05-14-iter-clippy-sweep.md