feat: add persistent server-client sessions

   Make herdr persistent by default.

   Launching herdr now starts or reattaches to a background session
   server. Clients can detach and reattach while panes and agent
   processes keep running. Session mode now supports multi-client attach,
   auto-detect startup, and a thin-client/headless-server split.

   This also refactors the large app, ui, input, pane, config,
   workspace, and persistence modules into smaller focused submodules,
   while preserving behavior and colocating tests with the code they
   exercise.

   Upgrade notes:
   - persistence mode is now the default
   - in-app quit detaches the current client instead of stopping the server
   - use `herdr server stop` to stop the background session
   - use `--no-session` for the old single-process behavior
   - default socket paths now live under the config directory

1 files changed, 4 insertions, 37 deletions

diff --git a/CONFIGURATION.md b/CONFIGURATION.md
index fac2dd57..3396cc33 100644
--- a/CONFIGURATION.md
+++ b/CONFIGURATION.md
@@ -53,7 +53,7 @@ example:
 prefix = "ctrl+b"
 new_workspace = "n"
 rename_workspace = "shift+n"
-close_workspace = "d"
+close_workspace = "shift+d"
 new_tab = "c"
 split_vertical = "v"
 split_horizontal = "-"
@@ -71,35 +71,6 @@ focus_pane_up = "alt+k"
 focus_pane_right = "alt+l"
 ```
 
-### custom command bindings
-
-custom commands also live under `[keys]`, but use repeated `[[keys.command]]` tables.
-
-each binding runs after pressing the prefix key and then the configured command key.
-
-actions:
-- `type = "shell"` launches a detached `/bin/sh -lc ...` command in the background
-- `type = "pane"` opens a temporary overlay pane, runs the command there, then restores the previous pane focus when it exits
-
-example:
-
-```toml
-[[keys.command]]
-key = "g"
-type = "pane"
-command = "lazygit"
-
-[[keys.command]]
-key = "o"
-command = "~/bin/herdr-open-current \"$HERDR_ACTIVE_WORKSPACE_ID\" \"$HERDR_ACTIVE_TAB_ID\" \"$HERDR_ACTIVE_PANE_ID\" \"$HERDR_ACTIVE_PANE_CWD\""
-```
-
-notes:
-- `type` defaults to `"shell"`
-- custom command keys share the same navigate-mode key namespace as built-in actions, so conflicts are rejected as config errors
-- `pane` commands require an active workspace and focused pane
-- shell commands inherit useful context through environment variables listed below
-
 ### key reference
 
 | key | default | action |
@@ -107,7 +78,8 @@ notes:
 | `prefix` | `ctrl+b` | enter or leave navigate mode |
 | `new_workspace` | `n` | create a new workspace |
 | `rename_workspace` | `shift+n` | rename selected workspace |
-| `close_workspace` | `d` | close selected workspace |
+| `close_workspace` | `shift+d` | close selected workspace |
+| `detach` | unset | optional explicit detach shortcut in the persistent session |
 | `previous_workspace` | unset | switch to the previous workspace directly from terminal mode |
 | `next_workspace` | unset | switch to the next workspace directly from terminal mode |
 | `new_tab` | `c` | create a new tab |
@@ -292,18 +264,13 @@ notes:
 - this matches Ghostty's default `scrollback-limit` value
 - set `scrollback_limit_bytes = 0` to disable pane scrollback entirely
 - the old `advanced.scrollback_lines` key is still accepted as a compatibility alias, but it uses the same byte-based value
+- in default persistence mode, quitting the ui detaches the current client; use `herdr server stop` to stop the shared background server
 
 ## environment variables
 
 | variable | description |
 |----------|-------------|
 | `HERDR_LOG` | log level filter (default: `herdr=info`) |
-| `HERDR_SOCKET_PATH` | socket path for `herdr` cli subcommands and scripts started from inside herdr |
-| `HERDR_BIN_PATH` | absolute path to the running herdr binary |
-| `HERDR_ACTIVE_WORKSPACE_ID` | active workspace id when a custom command is launched |
-| `HERDR_ACTIVE_TAB_ID` | active tab id when a custom command is launched |
-| `HERDR_ACTIVE_PANE_ID` | focused pane id when a custom command is launched |
-| `HERDR_ACTIVE_PANE_CWD` | focused pane cwd when available; shell commands also use it as their working directory |
 
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