initial first-push: cleanup + in-flight source work

First push to newly-created hyperpolymath/ipv6-only (private). Three
concerns combined into this single commit at user request:

1. Build-artefact purge: 570+ `target/` files removed from tracking.
   These were committed inadvertently by earlier sessions; the
   updated `.gitignore` now keeps `target/` out permanently.

2. `.gitignore` refresh.

3. In-flight source edits in:
   - `crates/core/src/lib.rs`
   - `crates/subnet/src/lib.rs`
   - `crates/utils/src/lib.rs`
   - `src/main.rs`
   These are unreviewed by tooling in this session; bundled here
   per user directive ("option 1 — commit everything together") so
   the GitHub repo has the current working-tree state as its initial
   main. If they contain anything worth splitting into cleaner
   commits, that can be done in follow-up PRs.

Sibling to hyperpolymath/ipv6-tools, /ipv6-site-enforcer,
/network-dashboard, /bgp-backbone-lab under the aerie umbrella.
Per estate policy 2026-04-17 (feedback_aerie_canonical_ambientops_subset),
a restricted/safer/more-automated subset of this tool will land in
ambientops via the to-be-implemented extraction pipeline.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.gitignore

@@ -77,3 +77,11 @@ htmlcov/
 /tmp/
 *.tmp
 *.bak
+target/
+node_modules/
+_build/
+deps/
+.elixir_ls/
+.cache/
+build/
+dist/

crates/core/src/lib.rs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MPL-2.0
 //! Core IPv6 types for ipv6-only
 //!
 //! Provides IPv6Address and IPv6Network types with full address manipulation.

crates/subnet/src/lib.rs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MPL-2.0
 //! IPv6 subnet calculator and network planning utilities.
 
 use ipv6_only_core::{IPv6Network, Ipv6Error, Result};

crates/utils/src/lib.rs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MPL-2.0
 //! IPv6 utility functions for address manipulation and generation.
 
 use ipv6_only_core::{IPv6Address, IPv6Network, Ipv6Error, Result};

src/main.rs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MPL-2.0
 //! ipv6-only CLI
 //!
 //! IPv6 address manipulation, subnet calculation, and network planning tools.