Allowlist the rebar3 verification loop in project settings

[david-w-t]

Adds five entries to .claude/settings.json → permissions.allow, covering the
commands that dominate permission prompts in this repo:

Bash(./rebar3 ct:*)
Bash(./rebar3 compile:*)
Bash(./rebar3 eunit:*)
Bash(./rebar3 xref:*)
Bash(make test-ct-parallel:*)

These are the project's verification loop. ./rebar3 xref in particular became a
CI gate in the SP2 branch, so it now runs on essentially every change.

Why these and not more

Derived from a scan of recent session transcripts. The large majority of the
Bash traffic in this repo needs no rule at all — read-only git and gh
subcommands, plus grep/head/tail/cat/ls/find/sed, are already
auto-allowed and were deliberately left out.

Excluded on purpose:

• Anything granting arbitrary code execution — ./rebar3 shell, bash,
  python3, erl, ssh. A wildcard Bash(./rebar3 *) would have covered the
  four entries above in one line but would also have allowed ./rebar3 shell,
  hence the four narrow prefixes instead.
• Mutating git commands — git add/commit/push/reset/fetch.
• Machine-specific paths. The plugin-cache script paths that account for the
  most prompts are user-local and stay in .claude/settings.local.json, which is
  gitignored — they have no business in a file other contributors receive.

No functional change to the codebase.

🤖 Generated with Claude Code

https://claude.ai/code/session_01EWukKCbrN8GybaScJGU2kF