feat(hosts): add GitHub Copilot CLI as 11th supported host

[Bharath-varma-p]

What

Adds GitHub Copilot CLI as the 11th supported host in gstack, following the declarative ADDING_A_HOST.md pattern. Closes the gap that opened in Copilot CLI v1.0.36 (Apr 24, 2026) when ~/.claude/ skills stopped being auto-loaded.

After this PR, users on the standalone copilot CLI can:

./setup --host copilot
copilot
> /skills list   # all 43 gstack skills, namespaced as /gstack-*

Why

• Issue Add GitHub Copilot CLI as a supported host #393 has 18 hearts asking for this.
• PR feat: add GitHub Copilot CLI as a supported host #1044 (sumitgogia, declarative pattern, also targets Copilot CLI) has been quiet for 5+ weeks; I left a coordination comment on it (feat: add GitHub Copilot CLI as a supported host #1044 (comment)) before opening this one. Credit to that prior work for setting the declarative direction.
• Copilot CLI now requires its own host root (~/.copilot/skills/) and rewrites Claude tool names to its own (Read -> view, Write -> create, Bash -> bash, Agent -> task, etc.).

How (4 commits, ~450 lines, 9 files)

1. feat(hosts): add GitHub Copilot CLI as 11th supported host

   • New hosts/copilot.ts declarative HostConfig
   • Registers in hosts/index.ts, bumps host count assertion (10 -> 11)
   • cliCommand: 'copilot' (the standalone npm @github/copilot binary, not the older gh copilot extension)
   • globalRoot: '.copilot/skills/gstack', localSkillRoot: '.copilot/skills'
   • frontmatter allowlist of {name, description} (strips Claude's allowed-tools array which Copilot's shell field would reject)
   • skipSkills: ['codex', 'pair-agent'] (codex is a Claude wrapper around codex exec; pair-agent depends on Claude streaming)
   • suppressedResolvers: REVIEW_ARMY, ADVERSARIAL_STEP, DESIGN_OUTSIDE_VOICES, CODEX_SECOND_OPINION, CODEX_PLAN_REVIEW, GBRAIN_* (these expand to Claude subagent_type blocks that don't translate)
   • boundaryInstruction scoped to FOREIGN home dirs only (~/.claude, ~/.codex, etc.); the repo-local .claude/skills/ is allowed since Copilot officially reads it.

2. feat(hosts): add tool name rewrites for Copilot CLI compatibility

   • Comprehensive toolRewrites covers 3 patterns per tool: use the X tool, the X tool, bare X tool (catches (Read tool), (via Agent tool) parenthesized usages).
   • Mapping: Bash -> bash, Read -> view, Write -> create, Edit -> edit, Agent -> task, Grep -> grep, Glob -> glob, AskUserQuestion -> ask_user.
   • WebSearch is intentionally not rewritten (semantically wrong: web_fetch retrieves URLs, not searches).
   • Verified post-rewrite: zero Read tool|Write tool|Bash tool|Agent tool|... substrings remain in the generated 47k-line ~/.copilot/skills/ tree.

3. feat(setup): add --host copilot install support

   • --host copilot validation, INSTALL_COPILOT plumbing, generation step (1e), helper functions create_copilot_runtime_root + link_copilot_skill_dirs, install dispatcher block (6d).
   • Mirrors the opencode pattern exactly.
   • Verified end-to-end: ./setup --host copilot linked 43 skills into ~/.copilot/skills/; copilot then shows them under /skills list.

4. docs(copilot): README install section, gstack-uninstall coverage, docs/COPILOT.md

   • README: bumps host count, adds Copilot row to the host table, adds dedicated install subsection (npm/brew/winget) with v1 scope notes.
   • bin/gstack-uninstall: adds ~/.copilot/skills/gstack* to the cleanup block and confirmation prompt (mirrors Kiro).
   • docs/COPILOT.md: integration guide with tool-name translation table, v1 scope rationale, custom-instructions location matrix, troubleshooting.

Differences vs PR #1044

I learned from #1044's groundwork; here are the deltas:

Concern	#1044	This PR
cliAliases	['gh']	none (the gh copilot extension is a different product; this is the standalone copilot binary)
Tool rewrites	2 patterns	3 patterns (adds bare X tool to catch (Read tool) parenthesized refs)
pair-agent	not skipped	skipped (depends on Claude streaming)
Orchestration resolvers (REVIEW_ARMY etc.)	inherited verbatim	suppressedResolvers (Claude subagent_type syntax doesn't run on Copilot)
WebSearch	rewritten to web_fetch	intentionally left alone (semantic mismatch)
localSkillRoot	.github/skills/gstack	.copilot/skills (avoids creating tracked-by-default git noise; Copilot reads .copilot/skills/ natively)
Branch base	~32 commits behind main	rebased on current main

Validation

• bun run scripts/host-config-export.ts validate -> "All 11 configs valid"
• bun test test/host-config.test.ts test/gen-skill-docs.test.ts -> 455 tests, 0 fail, 5623 expects
• bun test (full suite) -> 2217 pass / 8 fail. The 8 failures are pre-existing baseline (doc-inventory cross-check for AGENTS.md/skills.md, ship-version-sync VERSION/pkg drift, read_secret_to_env var-name validation, port-detection race tests). Zero regressions.
• Real install: ./setup --host copilot -> 43 skills linked into ~/.copilot/skills/; copilot -> /skills list shows them.
• bun run gen:skill-docs --host all -> 47074 lines, 541k tokens, no host-specific errors.

v1 scope (intentional)

This PR ships a focused v1. The following are deferred to a follow-up once Copilot CLI's orchestration story matures:

• Skipped: /codex, /pair-agent (Claude-streaming-specific).
• Suppressed orchestration resolvers (/review, /qa, /plan-*-review, /cso, /design-*, /setup-gbrain) still install but the Claude subagent_type blocks are stripped, so they run as single-pass sessions instead of fan-out reviews. docs/COPILOT.md documents this and points users to the Claude or Codex hosts if they need the multi-agent reviews.

Test plan for reviewers

git fetch origin pull/<this-pr>/head:copilot-pr && git checkout copilot-pr
bun install
bun test                         # confirm same 8 baseline failures, no new ones
bun run scripts/host-config-export.ts validate   # 11 configs valid
./setup --host copilot           # if you have Copilot CLI installed
ls ~/.copilot/skills/            # 43 entries
copilot                          # then /skills list

Acknowledgements

• Issue Add GitHub Copilot CLI as a supported host #393 reporter and the 5+ commenters who kept the demand visible.
• @sumitgogia for feat: add GitHub Copilot CLI as a supported host #1044, which validated the declarative direction; if you'd prefer to land this on top of feat: add GitHub Copilot CLI as a supported host #1044 rebased, I'm happy to coordinate.
• @ridermw for feat: add GitHub Copilot CLI support #396 / Add GitHub Copilot CLI support via Claude-compatible skills #487, which clarified the path/tool-name space.

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[vishnud05]

you should also add "copilot" at line 59 in setup file. there is a static check for all the agents in the setup file, and it is failing.