fix(benchmarks): use awk -v for variable passing to fix newline parse error

[anhermon]

Thinking Path

1. Anvil repo → benchmarks/run.sh provides build-quality scoring
2. PR feat: add benchmark suite for build quality scoring #51 (ANGA-593) added the benchmark suite but CI fails on the awk weighted-score calculation
3. Error: awk: cmd. line:3: unexpected newline or end of string — the multi-line awk expression breaks
4. Root cause: awk treats newlines as statement terminators; a trailing + operator before a newline has no right operand
5. The original code used double-quoted shell expansion (awk "BEGIN { ... $VAR ... }"), which is fragile — empty or newline-containing variables also break parsing
6. Fix: switch all awk calls to -v variable passing with single-quoted programs — portable, safe from shell injection, and avoids the newline issue entirely

What Changed

• benchmarks/run.sh: Replaced all 5 awk "BEGIN { ... $VAR ... }" invocations with awk -v var="$VAR" 'BEGIN { ... var ... }' pattern
  • normalize() fallback awk call (line 38)
  • TEST_PASS_RATE calculation (line 98)
  • BINARY_MB calculation (line 163)
  • OVERALL weighted score calculation (line 169) — primary fix for the reported error
  • PASS threshold check (line 179)

Verification

• bash -n benchmarks/run.sh passes syntax check (confirmed locally)
• bash benchmarks/run.sh completes without awk error
• benchmark-results.json is generated with valid JSON
• CI benchmark job passes

Risks

Low risk — this is a targeted fix to shell quoting in a single file. The awk -v pattern is POSIX-standard and more portable than double-quoted expansion. No behavioral change to scoring logic.

Checklist

• Commit messages follow Conventional Commits
• PR description explains the reasoning
• Co-Authored-By: Paperclip <noreply@paperclip.ing> in commit

Closes ANGA-601