Proposal: add Qoder as an install target (#256)

[nolanchic]

Proposal: add Qoder as an install target (#256)

Following the "discuss first" rule for new integration platforms — issue #256 tracks Qoder support and the checklist in CONTRIBUTING, and this is the alignment step before a PR.

What Qoder expects. Per the official subagent docs (IDE) and CLI subagents, an agent is one Markdown file with YAML frontmatter (name and description required, body is the system prompt), discovered from ~/.qoder/agents/<name>.md (user-wide) or <project>/.qoder/agents/<name>.md (project). The CLI resolves same-named agents user < project < plugin, and project-level agents require a trusted project folder. Qoder names its tools the way Claude Code does (Bash, Edit, Write, Glob, Grep, Read, WebFetch, WebSearch; the CLI adds Agent), and an omitted tools: means the full available set.

Proposed integration (mirrors the Qwen Code one, which is the same file shape):

• tools.json: one qoder entry, format: qoder-md (not shared with qwen-md, because we emit a tools: line Qwen output translates differently), installKind: per-agent, scope user + project, dest ~/.qoder/agents/{slug}.md / .qoder/agents/{slug}.md, QODER_AGENTS_DIR override, detected via the qoder binary or ~/.qoder.
• convert.sh: convert_qoder writes frontmatter name (slug) + description + body, and keeps the source tools: allow-list translated to Qoder's spellings (MultiEdit→Edit, Task→Agent; everything else already matches). Dropping it would silently hand restricted agents Qoder's full default tool set, which is why I'd rather not omit the field even though it's optional.
• install.sh: user-scoped by default, --path/QODER_AGENTS_DIR for a project, standard --division/--agent/--agents-file/--link/--dry-run filters, agent-md collision group.
• .gitignore: integrations/qoder/agents/; only integrations/qoder/README.md is committed.
• Tests: test-install.sh gains six Qoder cases (default dir, --path precedence over env, env dest + division filter, --agents-file, --dry-run); test-convert-outputs.sh gains a Qoden tool-name gate that fails if a source allow-list is dropped or maps to a name Qoder doesn't have.

Checks I ran: check-tools.sh (18 tools consistent), test-convert-outputs.sh 35/35 (283 agents × 16 tools), test-install.sh 77 passed / 0 failed / 2 known-xfail (#755).

Open questions before I open the PR:

1. Is a dedicated qoder-md format acceptable, or would you rather share qwen-md and accept the tools: spelling difference? The formats are byte-identical for agents without a tools: line.
2. Should the default install be user-scoped (~/.qoder/agents/)? Qwen defaults to the project directory; Qoder's docs lead with the user directory, and IDE users get the agents everywhere, so I went with user — easy to flip.
3. Icon: I set "icon": null per the "null unless the app ships a brand SVG" rule — the accent color is #615CED (Qoder's purple), same value as Qwen's, tell me if you want it distinguished.

Not verified: loading the generated files in a real Qoder install — no Qoder CLI on this machine, so format claims rest on the docs above.