Slice 5a: surface blocked egress attempts (DoD #1)

[Pal Lakatos-Toth (pallakatos)]

First slice in the Slice 5 egress polish + observability sequence. Closes Slice 5 DoD #1 ("`azureclaw egress blocked` lists every host the agent attempted that the enforcement layer refused").

The router has been populating an in-process `BlockedBuffer` from the forward proxy since S12.f — this slice exposes that buffer to operators without giving the agent any new wire access.

Producer (router)

• New `BlockedBuffer::snapshot_since(since_unix)` + `top_hosts(since, n)` methods. `snapshot_since` is newest-first by `last_seen_unix`; `top_hosts` aggregates across `(sandbox, port)` by hostname with a deterministic secondary sort for tied counts.
• 7 unit tests in `egress_blocked.rs` cover filter cutoffs, dedup count carry-through, multi-sandbox/multi-port aggregation, `n=0` early-return, and the `truncate(n)` contract.

Wire surface

```
GET /internal/egress/blocked?since=<rfc3339|unix|-Nm>
GET /internal/egress/blocked/top?window=&n=
```

Both mounted on the admin-gated `protected` router. JSON envelopes carry `schema_version: 1` and RFC 3339 strings alongside raw Unix seconds. Hand-rolled duration + RFC 3339 parsers (no `chrono` dep) with 7 unit + 6 integration tests covering bare seconds, `s/m/h/d` suffixes, relative `-Nm` form, malformed input → `0`, the `n ≤ 100` cap, and the default 5m window.

CLI

```
azureclaw egress blocked [--since 10m] [--top] [--window 1h] [--n 20] [--watch] [--json]
```

Added as a subcommand under `egress` so `--watch`/`--top`/`--since` don't collide with the existing flat-options surface. Mirrors `azureclaw inspect` token-resolution (`router-admin-token` secret first, in-pod `admin-token` file fallback) and uses in-pod `kubectl exec curl` to avoid port-forward collisions. `--watch` loops every 5s with VT clear; `--top` overrides `--since`; `--json` emits raw response.

13 vitest unit tests cover `buildPath`, the renderer surface (HOST/PORT/SANDBOX/LAST_SEEN/COUNT columns, empty-state message, since-filter line, top-N window line) and the `unixToIso(0) === "epoch"` sentinel.

Verification

• `cargo test -p azureclaw-inference-router` → 849 lib + 8 egress_blocked integration (up from 2)
• `cargo clippy -p azureclaw-inference-router --all-targets -- -D warnings` clean
• `cargo fmt --all` clean
• `npm test` → 692 CLI tests (up from 679; +13 new)
• `npm run typecheck` / `npm run build` clean

Principles compliance

• §5 no scaffolding — producer (BlockedBuffer fill from forward proxy) was already live; this PR connects consumer surfaces to it.
• §6 dev-only + test every new line — every new helper has unit coverage; every new endpoint has integration coverage; every new CLI helper has vitest coverage.