fix(install): macOS bash 3.2 crash and wrong download paths

[rebel117]

Problem

The installer (scripts/install.sh) has two bugs that prevent it from running on macOS:

1. declare -A crashes on macOS bash 3.2

macOS ships bash 3.2 by default, which doesn't support associative arrays. Running the script produces:

bash: line 36: sparc: unbound variable

2. Hardcoded Linux download paths

MINER_URL, FINGERPRINT_URL, and MINER_CRYPTO_URL all point at miners/linux/ regardless of OS. On macOS the script downloads the Linux miner and tries to download miner_crypto.py which doesn't exist in miners/macos/.

Fix

1. Replaced declare -A MULT_TABLE with a get_mult_value() function using a plain case statement — works on bash 3.2+
2. Added OS detection for MINER_SUBDIR so macOS gets miners/macos/rustchain_mac_miner_v2.5.py instead of the Linux miner
3. Made miner_crypto.py download conditional on Linux (macOS miner is self-contained)
4. Introduced MINER_SCRIPT variable so systemd/launchd service files reference the correct script name per platform
5. Bumped install.sh (root) macOS miner reference from v2.4 to v2.5

Testing

• bash -n scripts/install.sh — syntax OK
• bash -n install.sh — syntax OK
• Verified get_mult_value() returns correct values for all arch keys
• Confirmed no declare -A remains in either script

Fixes #7975

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Review of PR #7995 — macOS bash 3.2 Compatibility + Download Path Fix

Observation 1: MINER_URL still hardcodes rustchain_linux_miner.py even when MINER_SUBDIR=macos (scripts/install.sh)

The initial assignment on line 55 uses:

MINER_URL="${REPO_RAW}/miners/${MINER_SUBDIR}/rustchain_linux_miner.py"

When MINER_SUBDIR=macos, this resolves to miners/macos/rustchain_linux_miner.py — which is wrong. The subsequent if block corrects it to rustchain_mac_miner_v2.5.py, but the initial wrong URL is assigned first. While the if block fixes it, this creates a confusing code path. Consider setting MINER_URL conditionally from the start, or using a case statement to set all three URLs together.

Observation 2: declare -A replacement uses parallel arrays which may break if entries are reordered (scripts/install.sh)

The fix replaces declare -A with parallel arrays MULT_KEYS and MULT_VALUES. This works, but the lookup relies on matching indices. If someone adds an entry to one array but forgets the other, the lookup silently returns the wrong multiplier. Consider using a single case statement instead:

get_multiplier() {
    case "$1" in
        sparc) echo "2.9";; mips) echo "3.0";; 68k) echo "3.5";;
        g4) echo "2.5";; g5) echo "2.0";; g3) echo "1.8";;
        power8) echo "1.5";; riscv) echo "1.4";; retro) echo "1.4";;
        apple_silicon) echo "1.2";; modern) echo "1.0";; aarch64) echo "0.0005";;
        *) echo "1.0";;
    esac
}

This is more idiomatic for bash 3.2 and avoids the index-matching fragility.

Observation 3: The aarch64 multiplier 0.0005 seems suspiciously low

A multiplier of 0.0005 means aarch64 miners get 0.05% of the base reward. This is 2000x less than modern (1.0). If this is intentional (e.g. aarch64 is not yet supported), it should have a comment explaining why. If it's a placeholder, it could cause confusion for users who see nearly zero rewards on ARM64 Linux.

Positive notes

• The uname -s approach for detecting macOS is portable and correct.
• The macOS miner path version bump from v2.4 to v2.5 is clearly documented.
• The bash 3.2 compatibility fix is the right approach — associative arrays were only added in bash 4.0.

[Scottcjn]

You have two PRs doing the same macOS bash-3.2 installer fix — this one and #8005. #8005 is the cleaner implementation (single-branch OS resolution, graceful fallbacks), so let's consolidate there. Closing this in favor of #8005; I've left the specifics of the remaining CI failure on that one.