Track upstream registration of `wg` multiaddr protocol (0x01C7)

Context

This issue tracks upstream registration of the draft WireGuard (wg) multiaddr protocol introduced in PR #108.

• Closes the coordination gap left after removing author planning docs from the PR.
• Related: #107, PR #108, goodboy/tractor#483 (author's expanded plan).

Settled implementation semantics (py-multiaddr #108)

Property	Value
Protocol name	wg
Code	0x01C7 (decimal 455) — slot between noise (0x01C6) and shs (0x01C8)
Binary form	Exactly 32 bytes — raw Curve25519 public key; fixed size 256 bits; no length prefix
String form	Multibase base64url — u prefix (matches /certhash in go-/py-multiaddr)
Conversion from wg(8)	multibase.encode('base64url', base64.b64decode(key))
Example	/ip4/1.2.3.4/udp/51820/wg/urCzgw_sszhsg-SpR8V5IPmVnYPg2PliWW739_SWemwY

Open questions for upstream spec review:

• Canonical-only u prefix vs accept-any-multibase-and-normalize on decode
• Whether degenerate keys (e.g. all-zero) are a codec concern (suggest: no — length check only)

Upstream registration plan

Step 1: multicodec PR (do first)

Repo: https://github.com/multiformats/multicodec

Add one row to table.csv (sorted by code, between noise and shs):

wg,                             multiaddr,      0x01c7,         draft,      WireGuard tunnel endpoint - 32-byte Curve25519 public key

• Run table validation locally before pushing (make / npm test per CONTRIBUTING).
• PR body: link WireGuard cryptokey-routing docs, py-multiaddr PR #108 as first implementation, overlay use case from #107.

Step 2: multiaddr spec PR (link multicodec PR)

Repo: https://github.com/multiformats/multiaddr

1. Add one row to protocols.csv (sorted by code, after noise / 454):

   455,	256,	wg,	WireGuard tunnel endpoint (Curve25519 public key)
   

2. If requested by maintainers, add a short protocol description covering:

   • Binary: 32-byte fixed-size Curve25519 public key (no length prefix)
   • String: multibase base64url u<43> (44 chars total)
   • Rationale: / in standard base64 collides with multiaddr delimiter; multibase matches certhash precedent
   • Canonical composition: /ip{4,6}/<host>/udp/<port>/wg/<key>

Open this PR referencing the multicodec PR from step 1.

Step 3: Circle back to py-multiaddr

After upstream PRs land (or in parallel once numbers are reserved):

• Update multiaddr/codecs/wg.py docstring to point at upstream PRs instead of "speculative draft"
• Update PR #108 description / tick multicodec TODO
• Close this issue when both upstream rows are merged

Step 4: libp2p/specs (optional, later)

Only after multiformats registration: document how libp2p stacks use /…/wg/… for overlay/tunnel addressing (e.g. extend addressing/README.md). Not required for py-multiaddr merge.

Step 5: Cross-implementation follow-up (optional)

Propose the same protocol to go-multiaddr / js-multiaddr once spec rows land.

Checklist

• Merge py-multiaddr PR #108 (pending removal of gh/wg_spec_submission_plan.md)
• Open multicodec PR for 0x01C7
• Open multiaddr PR for protocol 455 / wg
• Update py-multiaddr docs after upstream lands

Start with the upstream multicodec table.csv entry and its local validation instructions, then inspect multiaddr's protocols.csv for the corresponding row. Review multiaddr/codecs/wg.py and the referenced PRs before opening either upstream PR. Done means both upstream registrations are merged and the py-multiaddr documentation and docstring are updated.