Condense the documentation and thin the server's comments

The markdown had accumulated a lot that was stale rather than wrong.
PLAN.md still described pi as the llama.cpp harness, a refcounted
LlamaServerManager, and a providers-by-hosts cross-product, all of which
were superseded or never built; it also carried a second copy of the HTTP
table that routes.rs owns. EXPLORER.md and TRANSCRIPT_CACHE.md held
implementation checklists for work that has since landed. AGENTS.md
restated most of PLAN.md's design instead of being the working-notes
layer it says it is. 3225 lines of markdown to 2180, with the stale
sections gone rather than reworded.

On the server, comments explaining what the code already says are out and
the ones recording a constraint, a measurement or an incident are kept but
cut to a few lines each: 5504 comment lines to 4586.

Four doc comments in session/mod.rs, and one each in process.rs and
usage.rs, had drifted onto the item above the one they describe --
functions were reordered without them, so `stop_session`'s doc sat on
`set_session_cwd`, `stat_of`'s on `struct Stat`, and `UsageMonitor`'s on
`type Cached`. Each is back on its own item.

routes.rs's module table also claimed later phases would add `/hosts`,
which setups replaced.

cargo test (127 passed), clippy --all-targets and fmt are clean.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

server/src/auth.rs

@@ -1,17 +1,15 @@
 //! Bearer-token auth for the entire HTTP surface.
 //!
-//! This server's API *is* remote code execution, so the token gates every
-//! route with zero unauthenticated endpoints -- the middleware is applied
-//! once around the whole router (including the fallback) in `main.rs`,
-//! never per-route, so a new route can't forget it. See PLAN.md's security
-//! section for the threat model; the short version is that the token gates
-//! LAN/tunnel-reachable RCE and is rotatable, and WireGuard makes it
-//! defense in depth rather than the sole gate.
+//! This server's API *is* remote code execution, so the token gates every route
+//! with zero unauthenticated endpoints -- the middleware is applied once around
+//! the whole router (including the fallback) in `main.rs`, never per-route, so a
+//! new route can't forget it. See PLAN.md's security section for the threat
+//! model.
 //!
 //! Nothing in this module -- and nothing anywhere else -- may log the
-//! Authorization header or the token; the test below holds a tripwire
-//! against a logging change silently starting to. It is one test covering
-//! both gating and logging on purpose -- see the note in it.
+//! Authorization header or the token; the test below is a tripwire against a
+//! logging change silently starting to. It is one test covering both gating and
+//! logging on purpose -- see the note in it.
 
 use std::net::SocketAddr;
 use std::sync::Arc;