P3: meta + primitive tool group (think/now/cite + classify/extract/summarize)

Grow executus/tools into a real generic tool library:

- Register(reg): the always-available, zero-config tools — think, now (UTC
  unless a CurrentTimeProvider is wired), cite (inert unless a CitationStorage
  is wired). All nil-safe; a light host calls Register and is useful.
- RegisterMeta(reg, MetaDeps): the LLM-backed meta tools — classify,
  extract_entities, summarize — over the llmmeta helper. Budget defaults to the
  shipped in-memory per-run cap; Files optional; caps default.
- Seams moved (interface/type-only, no host coupling): research_providers.go
  (CurrentTimeProvider/CitationStorage/SearchBudget/PageExtractor/PDFFetcher/…)
  and file_storage.go (FileStorage + FileDomainMeta). Plus the in-memory budget
  default (research_defaults.go) and scope_validate.go.

calculate deferred (drags github.com/Krognol/go-wolfram + a module-path replace
— not worth it in the lean core for one tool). Core go.sum still free of
gorm/redis/discordgo/sqlite/wolfram.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tools/now.go

@@ -0,0 +1,101 @@
+package tools
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"strings"
+	"time"
+
+	"gitea.stevedudenhoeffer.com/steve/executus/tool"
+)
+
+// nowParams is the LLM-facing param struct for current_time / now.
+//
+// Why optional `timezone`: most agent prompts know the user's local
+// timezone (it's in the chatbot's system prompt) but the agent has
+// no way to override on a per-call basis. An explicit arg lets a
+// research skill ask "what time is it in NYC for the user reading
+// this report?" without needing access to a member-config lookup
+// tool.
+type nowParams struct {
+	Timezone string `json:"timezone,omitempty" description:"Optional IANA timezone name (e.g. 'America/Chicago', 'Europe/London'). Defaults to the calling user's configured timezone, falling back to UTC."`
+}
+
+// nowResponse is the JSON envelope returned to the agent.
+//
+// Why a structured shape: the v1 tool returned a markdown blob.
+// Agents that needed just the year had to substring-parse, which
+// fails on locale variations. JSON lets the agent pick the field
+// it cares about.
+type nowResponse struct {
+	NowISO   string `json:"now_iso"`
+	NowHuman string `json:"now_human"`
+	Timezone string `json:"timezone"`
+	Weekday  string `json:"weekday"`
+	Year     int    `json:"year"`
+	Month    int    `json:"month"`
+	Day      int    `json:"day"`
+	Hour     int    `json:"hour"`
+	Minute   int    `json:"minute"`
+	Second   int    `json:"second"`
+	Warning  string `json:"warning,omitempty"`
+}
+
+// NewNow constructs the v11 current_time / now tool. The provider
+// supplies the calling member's configured timezone (per-user
+// localisation). nil falls back to UTC.
+//
+// V11 keeps the registered tool name "now" for back-compat with the
+// existing tool catalog tests AND adds the same tool surface under
+// the agent-facing description "current time". The design spec
+// called the tool "current_time" but the v1 registry already used
+// "now" — switching the registry name would break stored skills'
+// `tools` lists. Same name, expanded behaviour.
+func NewNow(provider CurrentTimeProvider) tool.Tool {
+	return tool.NewGatedTool[nowParams](
+		"now",
+		"Return the current time. Optional 'timezone' (IANA name e.g. 'America/Chicago'); defaults to the calling user's configured timezone or UTC. Returns ISO + human-readable formats plus structured year/month/day/weekday for time-relative reasoning. Use this BEFORE assuming a year — the agent's knowledge cut-off may differ from real time.",
+		tool.Permission{
+			AuthoringRequirement: tool.RequirementAnyone,
+			OperatesOn:           tool.ScopeGlobal,
+			SafeForShare:         true,
+			Categories:           []string{"utility"},
+		},
+		func(ctx context.Context, inv tool.Invocation, p nowParams) (string, error) {
+			tzName := strings.TrimSpace(p.Timezone)
+			warning := ""
+			if tzName == "" && provider != nil {
+				tzName = provider.UserTimezone(ctx, inv.CallerID)
+			}
+			if tzName == "" {
+				tzName = "UTC"
+			}
+			loc, err := time.LoadLocation(tzName)
+			if err != nil {
+				warning = fmt.Sprintf("unknown timezone %q; falling back to UTC", tzName)
+				tzName = "UTC"
+				loc = time.UTC
+			}
+			t := time.Now().In(loc)
+			out := nowResponse{
+				NowISO:   t.Format(time.RFC3339),
+				NowHuman: t.Format("Monday, January 2, 2006 at 3:04 PM MST"),
+				Timezone: tzName,
+				Weekday:  t.Weekday().String(),
+				Year:     t.Year(),
+				Month:    int(t.Month()),
+				Day:      t.Day(),
+				Hour:     t.Hour(),
+				Minute:   t.Minute(),
+				Second:   t.Second(),
+				Warning:  warning,
+			}
+			b, mErr := json.Marshal(out)
+			if mErr != nil {
+				return "", fmt.Errorf("now: marshal: %w", mErr)
+			}
+			return string(b), nil
+		},
+	)
+}