refactor(cli)!: one shared base config with per-surface overlays

`dsh` shipped two config trees that were 43 rows the same: apps/cli/cordis.yml
composed web as 74 flat rows, while the TUI booted examples/tui-agent/cordis.yml
whose single `@deepseek-ai/dsh-tui-demo` row mounted twelve plugins behind a
twenty-key pass-through Config. Neither file was what its location claimed —
apps/cli hardcoded the "example" as the product default and the "demo" bundle
was the application — and every capability change had to be made twice.

- apps/cli/base.cordis.yml holds the 43 shared rows; tui.cordis.yml and
  web.cordis.yml are patch lists stating only what differs per surface
- overlays apply as SIBLING patch lists at one include level, because include
  patches never cross an include boundary. Precedence: base < surface <
  (--config | personal ~/.dsh/config.yaml) < launcher flag/profile patches
- `--config` now applies an overlay INSTEAD OF the personal one, so a demo or
  test tree never inherits the user's route; new `--config-replace` boots a file
  as the entire tree (the old `--config` behaviour). Both survive /resume
- vendor/include: index each `insert`ed row as it is added so a later patch can
  configure or disable it. Upstream built the id index once before the patch
  loop, leaving every surface-only row — the whole TUI front door — silently
  unpatchable from user config. Logged as local modification 8
- session identity moves to dsh-agent-loop's CONFIGURED_AGENT_IDENTITIES_KEY;
  dsh-tui's MAIN_SESSION_ID_KEY is deleted (only the bundle read it)
- delete examples/tui-agent, examples/cordis-agent, packages/examples/tui-demo;
  TUI tests → apps/cli/tests, cordis e2e → packages/cordis/tool-cordis/tests,
  examples/code-mode survives as an overlay leaf
- `dsh web` gains --config, threaded into AppCLIEntry as an extra overlay

Three latent defects surfaced and are fixed here: the TUI captured the optional
sessionQuery service once at construction and could permanently disable /resume
when it won the mount race; the session-store root silently reverted to a
project-local ./.sessions; --config-replace was dropped by the resume handoff.

Verified by booting each tree through the real Loader (TUI 55 entries, web 75,
zero unsettled) rather than reading YAML. All eight terminal snapshots replay
byte-identically; 14/14 PTY smoke, 112/112 snapshots, 25/25 doc-sync, hygiene
and lint clean.

.agents/notes/implemented/feature/2026-07-28-dsh-guided-skill-session-commands.md

@@ -12,7 +12,7 @@ Two recurring flows begin with the user manually invoking one skill and answerin
 
 `dsh migrate` and `dsh upgrade` boot the ordinary TUI as a fresh session whose first turn auto-invokes a bundled skill (`dsh-migrate`, `dsh-upgrade`), exactly as if the user typed `/skill:<name>` and pressed Enter.
 
-The seed reuses the existing TUI skill path, not a new one. `createTuiChat` already has `invokeSkill(name, instructions)` — the code a typed `/skill:<name>` runs, including the "Unknown skill" notice. The launcher passes the skill name to the app through a new boot-context slot `INITIAL_SKILL_KEY` (`tuiInitialSkill`), mirroring `MAIN_SESSION_ID_KEY`/`TUI_GOODBYE_MESSAGE_KEY`: `ctx.provide` is the only channel from launcher argv into a Loader-mounted plugin. The TUI's `apply()` reads the slot and folds it into `config.initialSkill`; after `ui.start()` succeeds, `createTuiChat` fires `invokeSkill(config.initialSkill, '')` once when set.
+The seed reuses the existing TUI skill path, not a new one. `createTuiChat` already has `invokeSkill(name, instructions)` — the code a typed `/skill:<name>` runs, including the "Unknown skill" notice. The launcher passes the skill name to the TUI through a new boot-context slot `INITIAL_SKILL_KEY` (`tuiInitialSkill`), mirroring `CONFIGURED_AGENT_IDENTITIES_KEY`/`TUI_GOODBYE_MESSAGE_KEY`: `ctx.provide` is the only channel from launcher argv into a Loader-mounted plugin. The TUI's `apply()` reads the slot and folds it into `config.initialSkill`; after `ui.start()` succeeds, `createTuiChat` fires `invokeSkill(config.initialSkill, '')` once when set.
 
 **Freshness is gated in the launcher, not the TUI.** `runSkillSession` always mints a fresh session and provides the slot only when `resumeSessionId === undefined`, so a later `dsh --resume <id>` of that session is an ordinary TUI session with no re-injection. The TUI stays generic: it invokes whatever skill it is handed, once, at startup.
 
@@ -36,7 +36,7 @@ No keyless PTY snapshot: per the maintainer's scope call for this change, unit c
 
 **Support `--resume` on `migrate`/`upgrade`.** Rejected: these are one-shot guided entries. A resumed session is an ordinary TUI session reachable through the default surface's `dsh --resume <id>`; re-injecting the skill on resume would duplicate the first turn.
 
-**Read `INITIAL_SKILL_KEY` in the app bundle (like `MAIN_SESSION_ID_KEY`) rather than in the TUI's `apply()`.** Not needed: `initialSkill` is a TUI `Config` field consumed in `createTuiChat`, so folding the slot into config at the TUI entry keeps it beside the other launcher-owned runtime reads (`tuiResumeHost`, `tuiGoodbyeMessage`) and leaves the app bundle unchanged.
+**Read `INITIAL_SKILL_KEY` outside the TUI (as `CONFIGURED_AGENT_IDENTITIES_KEY` is read by `agent-loop`) rather than in the TUI's `apply()`.** Not needed: `initialSkill` is a TUI `Config` field consumed in `createTuiChat`, so folding the slot into config at the TUI entry keeps it beside the other launcher-owned runtime reads (`tuiResumeHost`, `tuiGoodbyeMessage`) and touches no other plugin.
 
 ## Consequences