Target scope: filter what gets recorded, not what gets proxied

The proxy captured and stored literally everything with no way to
exclude unrelated traffic - every CDN asset, analytics beacon, and
third-party tracker request on a real engagement pollutes history and
search right alongside the traffic that actually matters.

internal/scope: Rule{Enabled, Pattern, IsRegex} and InScope(rules,
host). A non-regex pattern matches by case-insensitive substring
against the host - "example.com" matches "example.com",
"www.example.com", and "api.example.com" alike, covering "this domain
and its subdomains" without inventing a separate wildcard syntax.
IsRegex mirrors the same toggle match-and-replace rules already use,
for one consistent mental model across both rule types in this tool.
An empty or all-disabled rule set means everything is in scope - the
behavior before scope existed at all, unchanged, so a fresh install or
a user who never opens the scope view keeps recording everything
rather than silently nothing.

Deliberately a recording filter, not access control: out-of-scope
traffic still proxies completely normally, reaching its destination and
the client exactly as before. internal/proxy's forward() already writes
the response to the client before record() ever runs, so the scope
check (new in record()) can only affect whether the exchange gets
stored, never whether it happens. Blocking out-of-scope traffic outright
would be a materially different, much riskier feature - a wrong scope
pattern could silently break the very traffic someone's trying to test,
which is a far worse failure mode than a noisier history. Repeat/Intrude
(recordRaw, a separate function from record()) deliberately don't go
through the scope check at all: a user explicitly resending or fuzzing
a specific request wants to see the result regardless of scope, which
exists to cut passive-capture noise, not second-guess a deliberate
action.

internal/store: new scope_rules table (CREATE TABLE IF NOT EXISTS, no
migration needed - it's a new table, not a new column on an existing
one) plus List/Add/SetEnabled/Delete, mirroring the existing
match-and-replace rules CRUD exactly. internal/ipc: scope_list/
scope_add/scope_delete/scope_toggle request types and matching Client
methods; scope_add validates a regex pattern compiles before persisting,
same reasoning and same fix as the earlier rules_save validation (an
invalid regex should be rejected up front, not silently never match at
apply time with zero feedback).

TUI: 's' from the history list opens scope management, mirroring the
Rules view's own list+form pattern but simpler (add-only, no
edit-in-place - a pattern and a regex toggle don't need a five-field
form, delete-and-re-add covers changing one).

Verified live in tmux against a running daemon: added a substring scope
rule for one host, sent requests to both a matching and a non-matching
host - the non-matching one proxied successfully (client got its 200)
but was never recorded, the matching one was recorded normally;
confirmed a Repeater resend of the excluded host WAS recorded despite
being out of scope; toggled the rule off and confirmed recording
resumed for everything; added and confirmed a regex-mode rule saves and
displays correctly; deleted a rule and confirmed the list returns to
empty ("no rules means everything is recorded").

go build/vet/gofmt/test/mod tidy all clean.

1 files changed, 36 insertions, 3 deletions

diff --git a/PLAN.md b/PLAN.md
index 4864012..a3ca810 100644
--- a/PLAN.md
+++ b/PLAN.md
@@ -272,12 +272,45 @@ Repeater request, say) is skipped rather than aborting the whole
 export - the status line reports how many, so a partial export is
 visible, not silent.
 
+Shipped since: target scope. `s` from the history list opens scope
+management - add/toggle/delete rules matching a host by substring
+(case-insensitive, so "example.com" matches "www.example.com" and
+"api.example.com" too, covering "this domain and its subdomains"
+without a separate wildcard syntax) or by regex, mirroring the same
+Match-text-or-regex toggle match-and-replace rules already use for one
+consistent mental model. No rules configured (or none enabled) means
+everything is recorded - today's behavior before scope existed at all,
+unchanged, so a fresh install or a user who never opens the scope view
+keeps recording everything rather than silently nothing.
+
+Scope only filters what gets recorded, not what gets proxied: an
+out-of-scope request still reaches its destination and its response
+still reaches the client completely normally (see `internal/proxy`'s
+`forward()` - the response is already written to the client by the
+time the scope check runs; skipping the record step only skips
+storage). This was a deliberate choice over blocking out-of-scope
+traffic outright, which would be a materially different, much riskier
+feature - an access-control mechanism, not a noise filter, and a wrong
+scope pattern could silently break the very traffic the user is trying
+to test. Repeater and Intruder deliberately bypass the scope check
+entirely (recordRaw, a separate code path from the passive-capture
+record()): a user explicitly resending or fuzzing a specific request
+wants to see the result regardless of scope, which exists to cut
+passive-capture noise (CDNs, analytics, trackers, unrelated third-party
+hosts), not to second-guess a deliberate action. Verified live: added a
+substring scope rule for one host, confirmed a request to a
+non-matching host still proxied successfully (200 response reached the
+client) but was never recorded, confirmed the matching host's requests
+were recorded, confirmed a Repeater resend of the excluded host WAS
+recorded despite being out of scope, confirmed toggling the rule off
+resumed recording everything, and confirmed both the substring and
+regex pattern forms save and match correctly.
+
 Still open from the expanded "worth considering" list: import (no path
 back in yet - HAR export was prioritized as the more common daily need,
 getting captured evidence OUT for a report or another tool, over
-bringing traffic IN), copy-as-curl, and scope/target filtering (to keep
-noise - trackers, CDNs, unrelated third-party hosts - out of history
-and search). All requested explicitly; none started yet.
+bringing traffic IN) and copy-as-curl. Both requested explicitly; not
+started yet.
 
 Skipped deliberately (from the research, matches this tool's stated
 scope): active/passive vulnerability scanning, plugin marketplace,