feat(#2097): migrate Augment onto EoS declarative adapter + settings.json MCP companion (ADR-1239)

Fold augment's runtime-literal conversion branches onto descriptor-driven
hostBehaviors and delete dead code:
- Site A (_applyRuntimeRewrites case 'augment'): the 4 ~/.augment dot-dir
  regexes now derive from getDirName('augment') via escapeRegExp (byte-
  identical; getDirName('augment')==='.augment') — no runtime literal.
- Site B (applyRuntimeContentRewritesForCommandsInPlace): the
  `if (runtime==='augment')` markdown-converter branch now reads
  runtime.hostBehaviors.commandBodyConverter and dispatches through a local
  COMMAND_BODY_CONVERTERS map (degrade-closed on unknown/absent name).
- Deleted dead `claudeToAugmentTools` map (zero refs; orphaned by ADR-1508
  single-sourcing) and the unreachable `else if (isAugment)` agent-conversion
  branch (augment ∈ _DESCRIPTOR_AGENTS_RUNTIMES → gated out upstream).
- Incidental orphan cleanup (no-defer): removed the equally-unreachable
  `else if (isTrae)` agent-conversion arm left behind by trae's already-merged
  migration #2094 (trae ∈ _DESCRIPTOR_AGENTS_RUNTIMES, same upstream gate).
  copilot/windsurf/codebuddy arms are removed by their own pending migrations.

UPGRADE 3 (transport:mcp): register the GSD companion MCP server in Augment's
settings.json under mcpServers.gsd (Augment hosts MCP in settings.json, not a
standalone file). mergeGsdMcpServerIntoSettings mutates the in-memory settings
object finishInstall already writes (gated on hostBehaviors.mcpCompanion===
'settings-json'); non-destructive + idempotent; symmetric uninstall removal.
settings.json is golden-excluded, so no golden change. UPGRADE 1 (named/
background dispatch) + UPGRADE 2 (settings-json hook bus, Claude dialect)
were already live in production — this adds tests exercising both.

Golden: byte-identical for all 16 runtimes (folds preserve regex behavior;
MCP lives in golden-excluded settings.json) — verified by a real double-install
tree diff. Tests: declarative-reference-augment (adapter/axes/fail-closed/
undocumented-sub-axes + source-grep guard scoped to conversion-logic branches)
+ augment-upgrades (dispatch negotiation, hook-bus live install, MCP add/
idempotent/preserve/uninstall). Matrix + connect-gsd-mcp-server + a stale
install-on-your-runtime hook-ownership claim corrected; changeset (Changed).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/how-to/connect-gsd-mcp-server.md

@@ -1,7 +1,8 @@
 # How to connect a host to the GSD companion MCP server
 
 This guide shows you how to make a MCP-capable host (Claude Code, Codex,
-OpenCode, VS Code, Antigravity CLI, Cursor, Cline, Hermes) drive GSD — run GSD
+OpenCode, VS Code, Antigravity CLI, Cursor, Cline, Hermes, Augment Code) drive
+GSD — run GSD
 commands and read/write `.planning/` state — through the companion MCP server,
 with no bespoke plugin.
 
@@ -28,6 +29,11 @@ host.
 
 - **Claude Code / Codex / Cursor / Cline / Hermes** — under the host's
   `mcpServers` object (project or user config).
+- **Augment Code** — under the `mcpServers` block of its own
+  `settings.json` (not a standalone MCP config file, unlike Antigravity)
+  — global at `~/.augment/settings.json`, project-local at
+  `.augment/settings.json`. GSD's installer configures this entry
+  automatically (`--augment` installs).
 - **VS Code** — in the workspace MCP servers list.
 - **Antigravity** — under the `mcpServers` block of its standalone
   `mcp_config.json` profile (not embedded in `settings.json`) — global at

docs/how-to/install-on-your-runtime.md

@@ -397,7 +397,7 @@ Qwen Code supports 15 hook events. GSD registers the following events automatica
 npx @opengsd/gsd-core@latest --augment --global
 ```
 
-Skills land in `~/.augment/skills/` and slash command definitions land in `~/.augment/commands/`. GSD installs skills, agents, and commands (`/gsd-phase`, `/gsd-ship`, etc.). No hook or statusline ownership.
+Skills land in `~/.augment/skills/` and slash command definitions land in `~/.augment/commands/`. GSD installs skills, agents, and commands (`/gsd-phase`, `/gsd-ship`, etc.). GSD's managed lifecycle hooks are registered into Augment's own `settings.json` `hooks` block (Claude hook event dialect, covering session-start, tool-use, and phase-boundary events) — no statusline ownership. #2097 also registers the GSD companion MCP server under `settings.json`'s `mcpServers.gsd` (see [Connect a host to the GSD MCP server](connect-gsd-mcp-server.md)).
 
 ---