Second plugin: paramminer, a Param Miner-style hidden parameter prober

For every distinct GET endpoint (deduplicated in-memory so revisiting
a URL doesn't rerun the whole wordlist each time), sends a fresh
baseline resend plus one probe per candidate from a ~40-entry wordlist
of parameter names real backends surprisingly often read even when
never part of any observed request (debug, admin, redirect, role,
token, and similar). A probe whose response differs from baseline by
more than a small threshold (body length, or a different status
outright) is a likely hit, tagged paramminer:hit with the parameter
name and both response sizes as evidence. Deliberately GET-only with a
modest wordlist, not exhaustive POST/JSON-aware probing - same "small
honest v1" reasoning as authcheck's single-identity simplification.

Same discipline as authcheck: speaks the wire protocol directly, no
internal/ipc import, proving PLUGINS.md's documented protocol is
actually sufficient on its own.

Found and documented two real, non-obvious net/http behaviors while
building this: Request.Write ignores the RequestURI field entirely
(confirmed directly - a deliberately stale RequestURI still produced
the correct output, since Write derives the request line from
Request.URL instead) and silently adds a default User-Agent header if
the cloned request didn't already have one. Neither affects
correctness here since baseline and every probe get identical
treatment, but both are worth knowing before reusing this resend
pattern elsewhere.

Verified live end to end: a real daemon, a real Python origin with a
genuinely hidden debug parameter that substantially changes the
response, and a control endpoint that's stable regardless of any extra
parameter - the hidden-parameter endpoint was correctly tagged with
exactly the right parameter name, the stable one correctly left alone,
confirmed via tag: search and visually in the TUI with the JSON-array
tag payload rendering correctly.

1 files changed, 3 insertions, 2 deletions

diff --git a/README.md b/README.md
index 4eace20..b23ba4e 100644
--- a/README.md
+++ b/README.md
@@ -70,8 +70,9 @@ the same socket the TUI itself uses - see [`PLUGINS.md`](PLUGINS.md).
   a badge in the history list, searchable via `tag:name`, viewable
   (`T` from detail view) with JSON data syntax-highlighted the same way
   a pretty-printed response is. See [`PLUGINS.md`](PLUGINS.md) and
-  `plugins/authcheck` for a real, working one (an Autorize-style
-  authorization checker).
+  `plugins/authcheck`/`plugins/paramminer` for real, working ones (an
+  Autorize-style authorization checker, a Param Miner-style hidden
+  parameter prober).
 - **Comparer**: mark one entry (`c`), then `c` on a different entry to
   see a colored unified diff of either side's request or response.
 - **Decoder**: standalone URL/Base64/Hex/HTML encode and decode (`d`),