Goblin: retire Nym from the public toolchains + drop internal test harnesses

- CI (release.yml/build.yml): remove fetch-nym + AWS_LC_SYS_PREBUILT_NASM;
  the default cargo build --release is Tor/arti only now (nip44 fetch kept).
- Cargo.toml: nym-sdk is optional behind the `nym` feature so the default
  build never pulls it.
- Delete the dead Nym-era probes (xrelay_smoke, connect_timing,
  tunnel_measure) that referenced the removed Nym API and broke `cargo test`.
- Untrack the internal E2E harnesses (e2e.rs, nostr_e2e.rs) via .gitignore;
  gate `mod e2e` behind the `e2e-internal` feature so clones still compile.
- Refresh stale Nym comments in build.rs and the build scripts.

.github/workflows/build.yml

@@ -1,12 +1,6 @@
 name: Build
 on: [push, pull_request]
 
-# aws-lc-sys (pulled in by nym-sdk) builds AWS-LC, which needs NASM on native
-# Windows. Use the prebuilt NASM objects the crate ships so the runner doesn't
-# need NASM installed; harmless on Linux/macOS.
-env:
-  AWS_LC_SYS_PREBUILT_NASM: 1
-
 jobs:
   linux:
     name: Linux Build
@@ -15,8 +9,6 @@ jobs:
       - uses: actions/checkout@v6
         with:
           submodules: recursive
-      # nym-sdk is a path dep on ../nym; materialize it before building.
-      - uses: ./.github/actions/fetch-nym
       # nip44 is a path dep on ../nip44; materialize it before building.
       - uses: ./.github/actions/fetch-nip44
       - name: Release build
@@ -29,7 +21,6 @@ jobs:
       - uses: actions/checkout@v6
         with:
           submodules: recursive
-      - uses: ./.github/actions/fetch-nym
       - uses: ./.github/actions/fetch-nip44
       - name: Release build
         run: cargo build --release
@@ -41,7 +32,6 @@ jobs:
       - uses: actions/checkout@v6
         with:
           submodules: recursive
-      - uses: ./.github/actions/fetch-nym
       - uses: ./.github/actions/fetch-nip44
       - name: Release build
         run: cargo build --release

.github/workflows/release.yml

@@ -25,8 +25,6 @@ permissions:
 
 env:
   TAG: ${{ inputs.tag || github.event.release.tag_name }}
-  # aws-lc-sys (via nym-sdk) needs NASM on native Windows; use its prebuilt NASM.
-  AWS_LC_SYS_PREBUILT_NASM: 1
 
 jobs:
   linux:
@@ -39,7 +37,6 @@ jobs:
         with:
           ref: ${{ inputs.tag || github.event.release.tag_name }}
           submodules: recursive
-      - uses: ./.github/actions/fetch-nym
       - uses: ./.github/actions/fetch-nip44
       - name: Build
         shell: bash
@@ -65,7 +62,6 @@ jobs:
         with:
           ref: ${{ inputs.tag || github.event.release.tag_name }}
           submodules: recursive
-      - uses: ./.github/actions/fetch-nym
       - uses: ./.github/actions/fetch-nip44
       - name: Build
         shell: bash
@@ -113,7 +109,6 @@ jobs:
         with:
           ref: ${{ inputs.tag || github.event.release.tag_name }}
           submodules: recursive
-      - uses: ./.github/actions/fetch-nym
       - uses: ./.github/actions/fetch-nip44
       - name: Build both architectures
         run: |