feat(host): books homes and starting an agent in one (P11b)

D-27: each book gets a visible folder, <Documents>/Wanderbooks/<id>, where an
agent works. It holds AGENTS.md and CLAUDE.md (three lines), the project-level
.mcp.json entry (wanderbooks mcp --book ID) and .claude/settings.json allowing
mcp__wanderbooks-ID__*, and nothing of the books: no data, key, token or path
into the data root (invariant I-1 stays: the books are hidden, not here). The
two JSON files are merged into and the text files written only when absent, so
a person's edits stay. Named by the book id, which never changes, not by the
company name, which is set after the books are made.

The viewer's New books... and wanderbooks connect make the home; connect_agent
is unchanged. start_agent says how to run Claude Code or Codex in it, or hands
back the vendor's installer (never bundled). Nothing is marked trusted for any
agent (Q-7: recommended answer, let Codex ask). First-run helpers (state, set
up the private folder, first owner passphrase) let the viewer onboard with no
terminal.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HS8WZziDnyxunC23MUxrLp

Cargo.lock

@@ -167,6 +167,31 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "alacritty_terminal"
+version = "0.26.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bda177466b9524d59f1b12f0dd30b68696788e9992a7e959021c4a0ed96fcf59"
+dependencies = [
+ "base64 0.22.1",
+ "bitflags 2.13.2",
+ "home",
+ "libc",
+ "log",
+ "miow",
+ "parking_lot",
+ "piper",
+ "polling",
+ "regex-automata",
+ "rustix 1.1.5",
+ "rustix-openpty",
+ "serde",
+ "signal-hook",
+ "unicode-width",
+ "vte",
+ "windows-sys 0.59.0",
+]
+
 [[package]]
 name = "alloc-no-stdlib"
 version = "2.0.4"
@@ -3049,6 +3074,15 @@ dependencies = [
  "digest 0.11.3",
 ]
 
+[[package]]
+name = "home"
+version = "0.5.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cc627f471c528ff0c4a49e1d5e60450c8f6461dd6d10ba9dcd3a61d3dff7728d"
+dependencies = [
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "http"
 version = "1.5.0"
@@ -3956,6 +3990,7 @@ dependencies = [
 name = "ledger-gui"
 version = "0.1.0"
 dependencies = [
+ "alacritty_terminal",
  "chrono",
  "eframe",
  "egui",
@@ -4370,6 +4405,15 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "miow"
+version = "0.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "536bfad37a309d62069485248eeaba1e8d9853aaf951caaeaed0585a95346f08"
+dependencies = [
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "moxcms"
 version = "0.8.1"
@@ -6226,6 +6270,17 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "rustix-openpty"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1de16c7c59892b870a6336f185dc10943517f1327447096bbb7bb32cd85e2393"
+dependencies = [
+ "errno",
+ "libc",
+ "rustix 1.1.5",
+]
+
 [[package]]
 name = "rustls"
 version = "0.23.45"
@@ -6612,6 +6667,16 @@ version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f8fadd59c855ef2080decdef8ff161eb6661b86933c9d82e5ba29dc602a55aba"
 
+[[package]]
+name = "signal-hook"
+version = "0.4.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b29ffa27d3d59a049bb328258de100f8012848d1b08d444e08bbc02ac468435e"
+dependencies = [
+ "libc",
+ "signal-hook-registry",
+]
+
 [[package]]
 name = "signal-hook-registry"
 version = "1.4.8"
@@ -8166,6 +8231,20 @@ version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5c3082ca00d5a5ef149bb8b555a72ae84c9c59f7250f013ac822ac2e49b19c64"
 
+[[package]]
+name = "vte"
+version = "0.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a5924018406ce0063cd67f8e008104968b74b563ee1b85dde3ed1f7cb87d3dbd"
+dependencies = [
+ "arrayvec",
+ "bitflags 2.13.2",
+ "cursor-icon",
+ "log",
+ "memchr",
+ "serde",
+]
+
 [[package]]
 name = "wait-timeout"
 version = "0.2.1"