fix(ci): retry forge solc fetch on transient DNS failures (#24358)

## Problem

PR #24352 (and others) intermittently fail in the merge queue with a DNS
error. The failing step is the `barretenberg/sol` test command:

```
Command: ...cd barretenberg/sol && forge test --no-match-contract Base
Error: error sending request for url (https://binaries.soliditylang.org/linux-amd64/list.json)
Context:
- Error #0: client error (Connect)
- Error #1: dns error
- Error #2: failed to lookup address information: Temporary failure in name resolution
```

`forge` reaches out to `binaries.soliditylang.org` to resolve/fetch the
solc binary. Under heavy parallel merge-queue load the VPC resolver
intermittently drops lookups (`Temporary failure in name resolution`),
and the operation fails with no retry, taking the whole CI run down with
it.

## Fix

Retry the solc-fetching `forge` operations **every 10s for ~5 min** (30
attempts), scoped to connection/DNS failures so genuine errors still
fail fast.

- **`ci3/retry`**: make the attempt count tunable via `RETRY_ATTEMPTS`
(default unchanged at 3); `RETRY_SLEEP` was already honored (default
5s). Fully backward-compatible — existing callers are unaffected.
- **`barretenberg/sol/bootstrap.sh`**: wrap the `forge test` test
command in `RETRY_ATTEMPTS=30 RETRY_SLEEP=10 retry -p '<dns/connect
regex>'`. This is the operation that fails in the merge queue.
- **`l1-contracts/bootstrap.sh`**: the root svm download (the "single
owner of the svm download") already had a short `retry`; extend it to
the same 10s/5-min window and scope it to DNS/connection errors.
(`2>/dev/null` removed so `retry`'s pattern matcher can see the DNS
error on stderr.)

The `-p` pattern (`dns error|Temporary failure in name resolution|error
sending request|failed to lookup address|Connection refused|connection
reset`) means a real `forge test` assertion failure or compile error is
**not** retried — it exits immediately, so this never masks real
failures or wastes 5 minutes on a genuinely broken test.

## Verification

Exercised `ci3/retry` and the exact emitted `barretenberg/sol` command
locally:

- DNS-matching failure → retries up to `RETRY_ATTEMPTS`, sleeping
`RETRY_SLEEP` between attempts.
- Real test failure (no DNS text) → fails fast, no retry (0s).
- Success → returns 0 on the first attempt (0s).
- `RETRY_ATTEMPTS` unset → still 3 attempts (backward-compatible).

---
*Created by
[claudebox](https://claudebox.work/v2/sessions/5610bcb5aef4d0b9) ·
group: `slackbot`*

Author: PhilWindle

barretenberg/sol/bootstrap.sh

@@ -19,7 +19,11 @@ function test_cmds {
 }
 
 function test_cmds_internal {
-    echo "cd barretenberg/sol && forge test --no-match-contract Base"
+    # forge reaches out to binaries.soliditylang.org to resolve/fetch solc, which intermittently
+    # fails DNS resolution under heavy parallel merge-queue load ("Temporary failure in name
+    # resolution"). Retry every 10s for ~5 min, but only on connection/DNS failures so genuine test
+    # failures still fail fast.
+    echo "cd barretenberg/sol && RETRY_ATTEMPTS=30 RETRY_SLEEP=10 retry -p 'dns error|Temporary failure in name resolution|error sending request|failed to lookup address|Connection refused|connection reset' 'forge test --no-match-contract Base'"
 }
 
 function build_sol {

ci3/retry

@@ -5,6 +5,8 @@ set -u # not -e
 # By default retries any non-zero exit. With "-p <regex>" only failures whose (combined) output
 # matches the extended regex are retried; any other failure exits immediately so genuine errors
 # (e.g. a real compile error) are not masked by retries.
+# The attempt count and the inter-attempt sleep are tunable via RETRY_ATTEMPTS (default 3) and
+# RETRY_SLEEP (default 5s), e.g. RETRY_ATTEMPTS=30 RETRY_SLEEP=10 retries every 10s for ~5 min.
 # Usage: retry [-p <retry-on-regex>] "<command>"
 pattern=
 if [ "${1:-}" = "-p" ]; then
@@ -18,10 +20,10 @@ if [ -n "${RETRY_DISABLED:-}" ]; then
   exit
 fi
 
-ATTEMPTS=3
+ATTEMPTS=${RETRY_ATTEMPTS:-3}
 out=
 [ -n "$pattern" ] && out=$(mktemp)
-# Retries up to 3 times with 5 second intervals
+# Retries up to $ATTEMPTS times, sleeping ${RETRY_SLEEP:-5}s between attempts.
 trap 'kill -SIGTERM $pid &>/dev/null || true; [ -n "$out" ] && rm -f "$out"' SIGTERM EXIT
 for i in $(seq 1 $ATTEMPTS); do
   if [ -n "$pattern" ]; then

l1-contracts/bootstrap.sh

@@ -20,9 +20,12 @@ function download_solc {
   mkdir -p "$HOME/.svm"
   # We build a minimal file to trigger svm download of solc. svm fetches the
   # binary from binaries.soliditylang.org, which intermittently fails to resolve
-  # under heavy parallel CI load; retry to ride out transient DNS drops. (The
-  # merge queue disables the cache above, so this download path runs every time.)
-  retry "forge build --use \"$solc_version\" src/core/libraries/ConstantsGen.sol 2>/dev/null"
+  # under heavy parallel CI load; retry every 10s for ~5 min to ride out transient
+  # DNS drops, but only on connection/DNS failures so a genuine build error fails
+  # fast. (The merge queue disables the cache above, so this download path runs
+  # every time. stderr is kept so retry can see the DNS error and match on it.)
+  RETRY_ATTEMPTS=30 RETRY_SLEEP=10 retry -p 'dns error|Temporary failure in name resolution|error sending request|failed to lookup address|Connection refused|connection reset' \
+    "forge build --use \"$solc_version\" src/core/libraries/ConstantsGen.sol"
 
   # Copy from svm cache to local path
   local svm_path="$HOME/.svm/$solc_version/solc-$solc_version"