security: untrack operations docs; scrub infra identifiers from public docs

Operations docs move out of git entirely rather than being sanitized. They
stay on disk for local use and are gitignored, so the Phase 6 export (which
takes HEAD) can never carry them. 15 files: the fleet runbook, hotfix
process, node inventories, internal trackers, session handoffs, the key
rotation/signing-posture records, and the open-source plan itself.

For the docs that remain public, infra identifiers are replaced with things
that are better documentation rather than placeholders: curl examples now
use `archipelago.local`, the product's own mDNS name, so a reader can run
them as-is instead of substituting an address that was never theirs.

Deliberately NOT scrubbed, both verified as functional rather than leaked:
- `tx1138.com` is the shipped default block explorer (DEFAULT_TX_EXPLORER in
  useTxExplorer.ts, surfaced in WalletSettingsModal). Product behavior.
- `git.tx1138.com` in core/container/{image_policy,registry}.rs is a retired-
  registry constant the code matches on to strip stale entries from legacy
  node configs. Removing it would break migration for older nodes.
- `192.168.1.254` in bulletproof-containers.md is the LAN gateway in a podman
  bug description, and `192.168.1.x` in user-walkthrough.md is already generic.

Whether a personal domain should be the shipped explorer default in a public
product is a separate product question, not a security one.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/bulletproof-containers.md

@@ -306,7 +306,7 @@ Ordered by likelihood × severity:
 2. Read failure-mode memory: `~/.claude/projects/-home-archipelago-Projects-archy/memory/feedback_container_lifecycle_failure_modes.md`
 3. Check task list for current release (should start with v1.7.41)
 4. Current state on fleet as of 2026-04-22:
-   - All 4 mirrors (tx1138, gitea-local, .160, .168) synced to v1.7.40-alpha
+   - All 4 registry mirrors synced to v1.7.40-alpha
    - .116, .198, .228, .253 healed manually via `systemd-run chmod 755 /opt/archipelago/web-ui`
    - .228 still has stale `bitcoin.conf` rpcauth (regenerated during triage; will drift again until v1.7.43)
    - .228 UI companions (archy-bitcoin-ui, archy-lnd-ui) keep vanishing (Quadlet migration in v1.7.45+ fixes)