fix: compose gate read the wrong directory; report CSS escape emitted the wrong glyph

[MyAlterLego]

Two bugs found while running a full-surface analysis against a large TypeScript monorepo (~3,600 files, 35 control actions, 140 cells). Both were hit in the course of a normal stpa run, and one of them put a false banner on a finished report, which is why I'd treat it as the more urgent of the pair.

1 · ComposeChains.ts discarded its own directory argument

argv.find((a) => !a.startsWith("--") && a !== argv[depthArg + 1])

With --max-depth absent, depthArg is -1, so argv[depthArg + 1] is argv[0] — the positional directory itself. It was filtered out of its own lookup and dir fell back to ".".

stpa run calls compose without --max-depth, so the gate read the current working directory, found no remediation.json, and printed:

missing remediation.json in <cwd> — run `stpa plan` first
!! UNRATED COMPOSITION (exit 1).

…against an analysis whose composition was fully rated (0 upgrades, 0 band changes when invoked with an explicit --max-depth). A gate reporting a failure it did not observe is worse than one that stays silent, because the banner it stamps on the report is false — and this gate exists precisely to stop an under-rated band reaching a reader.

Guarding on depthArg !== -1 changes behaviour only in the two broken cases. Verified across argv permutations:

argv	before	after
["dir","--check"]	.	dir ✅
["dir"]	.	dir ✅
["dir","--check","--max-depth","4"]	dir	dir
["--check","--max-depth","4"]	.	.
["--max-depth","4","dir"]	dir	dir
[]	.	.

Note the fourth row: "4" is still correctly not mistaken for the directory.

2 · The disclosure-triangle escape never reached CSS

content:"\25B8"      // inside the `html` template literal

\25 is consumed by the JavaScript parser before CSS sees it, so the emitted stylesheet never contained \25B8 (U+25B8 ▸). Where a parser accepts it as a legacy octal escape it yields U+0015 followed by the literal B8, making the rule content:"\x15B8" — a control character instead of a marker. Template literals also forbid legacy octal escapes outright, so a spec-compliant parser rejects the file at parse time rather than mis-rendering it, which is how it surfaced.

Doubling the backslash emits \25B8 into the stylesheet. Verified in a rendered REPORT.html.

One honest caveat, stated in the commit too: I could not exercise this under Bun in the environment where I found it, so the "what Bun renders" claim is derived from escape semantics rather than observed. The emitted-CSS fix itself is verified.

Deliberately not included

• A bun→node shim I used locally. That's an environment workaround, not a toolkit change, and CONTRIBUTING.md is explicit that this is a Bun project — making it runtime-agnostic is a scope decision for you, not something to smuggle into a bugfix PR.
• Tools/UcaGrid.ts readJson() calls Bun.file(path) and then discards the result (void f) while reading via fs.readFileSync. Harmless dead code, but it's the only thing forcing a Bun global in that file. Happy to strip it in a separate PR if you want it gone.

No dependencies added; no behaviour changed beyond the two defects.