fix(installer): stop duplicating agent instructions; MCP server is the single source of truth (#529) (#538)

The installer wrote a `## CodeGraph` usage block into each agent's
instructions file (CLAUDE.md / AGENTS.md / GEMINI.md / .cursor/rules /
Kiro steering) that duplicated, almost verbatim, the guidance the MCP
server already emits in its `initialize` response — so agents that
surface MCP instructions (Claude Code) read the same playbook twice
every turn.

All 6 instruction-writing targets (claude, cursor, codex, opencode,
gemini, kiro) now stop writing the block. install self-heals by
stripping a block a previous version wrote (uninstall already did), so
the next `codegraph install`/`uninstall` cleans up existing installs;
upgrading the package alone does not (the leftover block is harmless).
server-instructions.ts is now the single source of truth — the two
steers unique to the old template ("trust codegraph, don't re-verify
with grep" and the not-initialized -> `init -i` hint) are ported there.

Removes the now-dead INSTRUCTIONS_TEMPLATE / CLAUDE_MD_TEMPLATE,
claude-md-template.ts, writeClaudeMd / hasClaudeMdSection, and the
Cursor-only wireProjectSurfaces bootstrap. The install log learned a
"Removed" verb. Tests rewritten to the new contract + self-heal
coverage (140/140 installer tests pass).

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/mcp/server-instructions.ts

@@ -56,6 +56,7 @@ of calls; a grep/read exploration is dozens.
 
 ## Anti-patterns
 
+- **Trust codegraph's results — don't re-verify them with grep.** They come from a full AST parse; re-checking with grep is slower, less accurate, and wastes context.
 - **Don't grep first** when looking up a symbol by name — \`codegraph_search\` is faster and returns kind + location + signature.
 - **Don't chain \`codegraph_search\` + \`codegraph_node\`** when you just want context — \`codegraph_context\` is one round-trip.
 - **Don't loop \`codegraph_node\` over many symbols** — one \`codegraph_explore\` call returns them all grouped by file, while each separate call re-reads the whole context and costs far more. Use \`codegraph_node\` for a single symbol.
@@ -63,6 +64,7 @@ of calls; a grep/read exploration is dozens.
 
 ## Limitations
 
+- If a tool reports the project isn't initialized, \`.codegraph/\` doesn't exist yet — offer to run \`codegraph init -i\` to build the index.
 - Index lags file writes by ~1 second.
 - Cross-file resolution is best-effort name matching; ambiguous calls may return multiple candidates.
 - No live correctness validation — that's still the TypeScript compiler / test suite / linter's job. Codegraph supplements those with structural context they don't have.