Fix env.sh: portable CLUSTER_DIR, regex, and quoting issues

[rustyrazorblade]

Fix all shell scripting issues identified in env.sh:

• Replace realpath with portable cd && pwd approach for CLUSTER_DIR detection (works with source cluster/env.sh)
• Fix ZSH path detection using ${(%):-%x} prompt expansion instead of $0
• Fix incorrect regex in all flame functions: db[0-9*] to ^db[0-9]+
• Quote variables in ssh/rsync calls

Fixes #488

Generated with Claude Code

[claude]

Good set of targeted fixes. Here is my review.

[claude]

Good set of targeted fixes. Here is my review:

Regex fix is the most impactful change. The original db[0-9*] was genuinely broken: inside [...], * is a literal asterisk, so it matched db followed by one digit OR a literal *. The fixed ^db[0-9]+ (anchored, one-or-more digits) is correct and matches what the error message already described.

Portable CLUSTER_DIR - The cd and pwd pattern is the standard POSIX-portable alternative to realpath and correctly handles the source cluster/env.sh use case.

ZSH path detection - The ZSH percent-x idiom is the right ZSH way to get the path of the currently executing or sourced script. Better than dollar-zero, which returns the shell name when sourced.

Quoting - quoting the ssh host variable and the rsync remote host variable is correct. Quoting the rsync remote path as a single argument is exactly right.

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Two pre-existing issues worth a follow-up (not introduced by this PR, not blocking):

1. Empty HOST does not exit early in the flame functions. After printing the error, execution falls through to the regex check and prints a second message. Adding return 1 after the echo would fix this.

2. Unquoted SSH_CONFIG in the rsync alias (line 27): command rsync -ave with ssh -F SSH_CONFIG. If the config path ever contains spaces, the -e argument breaks. The inner string should quote SSH_CONFIG.

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All four changes are correct. The regex fix closes a real functional bug. No concerns with the implementation.

[github-actions]

Code Coverage

Total Project Coverage	67.03%	❌

[rustyrazorblade]

@claude rebase

[claude]

Claude finished @rustyrazorblade's task in 19s —— View job

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[claude]

PR Review - env.sh portability fixes. The regex, quoting, and CLUSTER_DIR changes are all correct. Three concerns: (1) EASY_DB_LAB_REBUILD=1 is now silently ignored - the flag semantics inverted to EASY_DB_LAB_SKIP_BUILD=1, which is a breaking change worth documenting. (2) EASY_DB_LAB_SKIP_DOCKER conflicts with the project never-disable principle in CLAUDE.md - the end-to-end tests would skip the full docker compose startup path. (3) All five flame functions are missing return 1 after the empty-HOST error message, so ssh runs with an empty host - worth fixing here. Pre-existing: c-dl has a hardcoded cassandra path /mnt/db1/cassandra/artifacts/ which conflicts with the general-purpose db tool principle.