feat(scripts): lint.lg — flag breadcrumb and devlog comments

[mparrett]

Requested in review on #735 — "We need a linter that checks for breadcrumbs and dev logs in comments" — and tracked as #835.

A devlog comment narrates the change instead of the code: the shape the code had earlier, what a reviewer asked for, what a later change will do to it. It reads as current, goes stale as soon as the change lands, and what it carries belongs in the PR body, a design doc, or the issue tracking the follow-up. There are some on main today; they are listed below.

What this adds

scripts/lint.lg, run the way the rest of the let-go tooling in scripts/ is run:

lg scripts/lint.lg [paths...]        # default: pkg scripts

It is written in let-go, alongside generate.lg, lgbdump.lg, and ir-stress.lg. Comments never reach the reader's form tree, so this is a raw-source pass over whole-line comments in .lg and .go, which also gives each finding an exact file:line instead of an enclosing-form anchor.

Report-only: it never edits source, and it always exits 0.

The phrase list

Deliberately small, and limited to wordings that can be true of the change but not of the code. "previously", "originally", and "for now" are left out because they read the same either way.

Matching is on whole words over normalized prose. Without that, this pr also matched "this process" and "this primitive": 49 findings over pkg/ collapsed to 13 once word boundaries were in and the over-firing no longer was dropped.

Comments carrying a licence header, a tool directive, or lint:ignore are skipped.

Verification

Against the review that prompted it, over the six files of #735 before and after that PR's comment cleanup:

	findings
before the cleanup	4, including the header the review comment anchored on
after the cleanup	0

On the current tree it reports 13 across 564 files. Three are unambiguous — shipped code pointing at a pull request that merged long ago:

pkg/nrepl/server.go:297        same hazard this PR fixes for the CLI REPL
pkg/resolver/resolver.go:289   losing the source snippet and stack this PR restores
pkg/ir/lisp_lower_go_test.go   the miscompile this PR fixes

pkg/rt/core/ir/ops.lg:33 carries (moved from typeinfer.lg's infer-one arms), and pkg/rt/lang.go:412, pkg/cli/wasm.go:131, and pkg/vm/var_deref_bench_test.go:15 are the same shape.

I read 11 of the 13 closely: nine I would call real, two I would not. pkg/ir/spike_rpnvm_test.go:128 describes a transformation the pass performs at runtime rather than a change to the code, and cmd/lginterop/main.go:82 is about deps.edn's history rather than this file's.

Open questions

These are why it is a draft.

• The phrase list is a starting point. You asked for the rule, so the wordings should be yours to set.
• Report-only, or a gate? Nothing here is wired into the Makefile or CI.
• Whether the findings above get fixed here or in a follow-up.