fix(tools): make write/edit's implicit lex check attest itself

[alpibrupa]

Summary

• write and edit already run lex fmt + lex check internally via linter.run, but that pass is a plain proc.run inside the tool's own body — invisible to lex-llm's dispatch_one_traced, which only sees separately-dispatched tool calls whose own result indicates a pass.
• A model that leans on this implicit check-and-repair loop (common under load — a smaller model, a truncated response, a tool-count squeeze per The local-model toolset is sized by guess, not measurement #87) produces correct, type-checked code that a task spec's verified.type_check criterion still reports unmet, for reasons that have nothing to do with correctness. Reproduced live via Ship the eval harness scoped in #86 #115's eval run across three providers on the same two tasks.
• linter.record_verified now writes a verified.type_check record directly to .lex/verified.jsonl (reusing the existing kind so no task spec needs to change) whenever a .lex file's implicit check passes, tagging tool: "write"/"edit" to keep provenance honest against the existing lex_check tool's own records.
• mkdir -p .lex runs first via proc, not std.fs, since Tool.execute's row is fixed at [net, io, proc] (record-field effect rows unify by equality) and this call happens from inside write/edit's execute — a fresh project (no prior memory-consolidation cycle, e.g. every eval-harness worktree) has no .lex/ directory yet, and verification.append_all's plain io.write into a missing directory fails silently once its Result is discarded.

Fixes #90

Test plan

• lex check on all three modified files, plus a full repo sweep (lex check over every tracked src/ file)
• lex fmt --check src/
• lex test (4/4 passing)
• lex doc-sync --check
• Live end-to-end verification: in a fresh git worktree with no .lex/ directory, invoked write.execute directly and confirmed .lex/verified.jsonl is created with {"kind":"verified.type_check","tool":"write","target":"verify_target.lex","ts_ms":0} — no separate lex_check tool call involved
• Confirmed git status clean of stray worktrees/artifacts after verification

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